Known Bugs (Apocalypse)

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Cityscape bugs

Firing Infatuated Agents

This happens if you have more than twenty combat agents (or biochemists, or engineers, or quantum physicists) assigned to single base. Only the first twenty specialists are visible in the hire/fire interface. The others cannot be fired from the agent interface.

Firing specialist (agent, biochemist, engineer or physicist) #1 fires agent #21 (and engineer #21 if present, and quantum physicist #21 if present) as well. Firing specialist #2 fires agent #22 (and engineer #22 if present, and quantum physicist #22 if present) as well.

And so on.

To fire >#20 specialists one needs to "transfer" some <#20 specialists to other base. Then it's still only possible to fire only first 20 specialists, but those which were further down the line are now visible. This can be done without unpausing - so it's possible to transfer those specialists back once proper guys/gals have been fired.

Rendor Plasma Shot Undercount

Per NKF's research ( http://www.xcomufo.com/forums/index.php?showtopic=242028127 ), the Rendor Plasma gun (an air vehicle weapon) actually has all 140 of the shots it used when loading up. The game divides this by two, reporting 70 shots.

Is that base yours ?

When aliens get to your base by spreading through the tubes, the game treats your base as if it was a building owned by the government. Hence, the alien activity will start growing on the government, if aliens are spotted you will have an alarm, and if you start a mission, you will combat in a standard warehouse or slum scenario, rather than in your base.

  • Possibly not a bug since it appears that X-COM bases are located underground, i.e. in the basement levels of said buildings.

Battleship ex nihilo

One of the Infiltration fleets (#17 on the UFO Incursions page) consists of one Battleship that inserts aliens, one Escort Ship, and one Battleship that bombs a building. This is the only UFO fleet in the game that has the same UFO type performing two different missions, and as such it runs afoul of a bug in the spawn routine. See, when checking whether there are enough UFOs for a fleet, the game checks for the presence of each UFO group separately, and the two Battleships are in different groups. As such, the game checks for whether there is 1 Battleship, 1 Escort Ship and 1 Battleship, not whether there is 1 Escort Ship and 2 Battleships, and may erroneously spawn this fleet (with both Battleships) even if there is only one Battleship in the Alien Dimension.

Time Lapse

If too many vehicles are on the Cityscape at the same time, you cannot choose the "Ultra Fast" time control option. This usually happens on the biggest Mega-Prime map on Superhuman where, due to the way some roads are connected in a criss-cross pattern with eachother, sometimes vehicles get stuck moving in circles eternally or if in one of those criss-cross sections of the map one exit was destroyed during UFO fights the vehicles will be unable to pathfind another way out, as they seem to try and always go for the shortest path, even if that one is destroyed, and will never try to go for an alternate longer path, regardless if one is available or not. To solve this issue, you have to use an X-Com Craft to either directly destroy some of the vehicles or use the Manual Craft Control (M to activate, LMB to shoot) to destroy the road/bridge the vehicles are on (no reputation loss).

65535 Widget Bug

You may sometimes find a store item with an unusually high count of 65535 or close to that amount. This bug occurs when the item count somehow goes into a negative value. Because item counters are instanced as unsigned integers, the negative will wrap back around to the highest value that it can hold. In this case, 65535.

One such example of how this could occur is when shifting an unresearched alien artefact that is instanced in both the air and ground transfer screens. If the item sliders are not locked and can be moved independently, you may be able to send more items than you physically own and put the store count into the negative.

Note that the user interface will properly report the negative count before you commit the item transfer.

With 65535 instances of any single item, this bug can easily be used as a money exploit.

Storage alchemy

When you sell off all of an alien artifact and it disappears from the sell screen, the game doesn't always re-point your stores correctly. One known possibility is all your Elerium-115 (potentially several hundred) being transmuted into GLM Air Defenses when Cloaking Fields are sold off.

This has been tested has it has nothing to do with alien artifacts or any ammo in particular. This is an error in the update routine when selling off the first item in the list of craft specific items to a zero storage quantity. If you buy a Light Weapons Control the game will give you the correct amount and your list will work as normal. If you happen to sell all the light modules, the quantity amounts (but not item list) of all your items in the Ground Vehicle section (even though you may have sold it in the Air Vehicle section) will be bumped down the list once. The second quantity of the item, that being Medium Weapons Control modules, will be inserted as the third quantity as well! eg: if you have seven medium modules and the repeatable bug appears, then will now have seven heavy modules as well - as long as the technology has been introduced. Repeatable (and exploitable): If you buy all the light modules again (and wait for delivery) and then sell them all, the quantity values will bump down once again!
Tested with a game around week four, multiple xcom bases, lots of mixed vehicles. Tested as such that it works exactly as mentioned. Others may find slight variations of this bug (which wouldn't be surprising).
Not to be confused with the 65535 Widget bug which is seperate.

Crazy transportation

If you hire new men and the road to access your base is broken, your men will pick a car but will not be able to reach the base and will keep turning around and around. But as soon as you set the "ultratime" on he will get to the base regardless the road was repaired or not.

No music bug

Whenever you save a game or sometimes when you end a battlescape mission, the music seems to stop playing. However, all that happens is that the music volume gets set down to 1 during the post battle screen or when you save the game, and fails to set itself back to its previous value. (you can still hear the music if you listen closely)

There are 4 ways of solving this:

1. Enter the options screen and simply uncheck and check the master volume slider.

(this will cause the current music track to get skipped or start from the beginning)

2. Move the master volume slider a bit to the left/right and then back to your desired position.

(this will prevent the track from being skipped / starting from the beginning)

3. Wait until the next music track plays, the volume will be correct with the next track playing.

(you might have to sit through 2-3 mins of silence)

4. Playing with the original CD reduces but not fully removes this bug. During the CD access to play the next track the volume usually gets set back to its proper value.

UFO Incursion - Battle Music

Usually you only get an eerie/slightly more worrisome music track playing (Uneasy Calm / The Infestation) during UFO incursions and rarely the battle music (Kill them ALL / Chase) will play.

This is most likely intended design, as the more hype battle music will only play during Apocalypse missions and only if enough UFOs are present. Around 5-6 UFOs minimum are required for the game to play the more threatening sounding tracks. It'll also continue playing as long as enough downed UFOs are still present on the map. Once you recover the wracks and the number of present UFOs on the Cityscape falls below the 5-6 threshold, the music will change back to Uneasy Calm/The Infestation and then back to normal, once all UFOs are recovered/expired.

Due to this, the more hype battle music can and will play regardless of the UFO incursion mission, as long as enough UFOs appear. Though it is most likely meant to only play during the Apocalypse mission.

Vehicle Repair Bay Placement in Starting Base

The starting base may have a bizarrely placed Vehicle Repair Bay. In the case shown below, it also takes up the two "empty" squares to the lower-left of the Access Lift.

Tactical section bugs

Poor pathway finding

The pathway finding algorithm will choose very poor paths when you move your men in the turn based version of the game. The path chosen will be OK only if you your men can reach their destination following a straight path and there are no obstacles around. Otherwise it will pick very crazy routes. The behaviour of the algorithm is particularly crazy when you are using flying units and more complicate routes can be chosen. Also, the path that your men follows when you move appears to be different from the one selected to predict the TUs left after the move, so that this prediction is often incorrect.

Agents travelling in time

When you start a mission in turn based mode, the clock will advance by a few seconds after each turn. But after that you have completed the mission it will get back to the time before mission started. The odd part is that the ship carrying the agents is ready to take off.

Quarreling with Transtellar is dangerous!

If you happen to upset Transtellar your men will not be able to move using transtellar cars. If you hire some men they will try to get to your base through the tubes, but they often will not be able to get to your base and remain stuck in another building. At this point if you then succeed into getting a better relationship with Transtellar, your men will not immediately get to your base, and some of them might remain stuck into their positions even running the ultratime. One way to unlock the agents is to transfer them temporarily to another base, another is to order the agent to any nearby building and then send a vehicle to pick them up.

Visual glitches

There are some glitches when you move your men flying very high, especially if tall structures are around. You will see "shadows" to appear and move here and there, and, after movement is completed, they will not be cleared until you force a complete redraw of the screen.

Resistance bug

In the turn-based mode when you are flying with the marsec armour at high speed (running) the stamina is unaffected, so that you can run as long as you like and each move has a reduced TUs cost. But if you run out of stamina everything works as if you were walking: the TUs cost of your movements is increased.

Spying capabilities

In turn based mode if you spot one or more aliens and you end your turn, the first steps of the alien that moves first (among the ones that you have spotted) are always visible, regardless that the alien is outside of the visual range of any of your men.

Big aliens visibility bug

Big aliens (Megaspawn, psymorphs) might not be visible to your men if part of their body is hidden behind structures. Even if the alien is sitting in front of you and half of its body is in sight.

Items limit in tactical combat

There seems to be a limit of items in tactical combat (roughly 500). If one takes a full contingent - 36 agents - to a combat, if there's too much equipment in their inventory some agents may not spawn and/or aliens (Anthropods and Skeletoids) may spawn without equipment. This *may* be a good exploit for dangerless tactical missions, but it will *not* give any points/credits for equipment that is missing - since it's not present.

Ammunition consolidation bug

In the agent equipment screen during tactical combat, ammunition can be combined by picking up an ammunition clip and then dropping it onto the same type of clip held in the inventory.

This is not necessarily a bug and likely intended to allow the player to consolidate partial clips such as those used in multi-munition weapons.

What is most likely unintended is that no bounds checking is performed to ensure that the target clip is only refilled to its maximum capacity. Instead the ammunition count for both clips are combined onto the target clip. The held clip on the other hand will be left with a count of 0.

This process can be repeated several times to consolidate multiple clips into a single large clip that only takes up the space of one.

This is a storage space exploit only. The game will still calculate the correct weight of the gestalt ammo clip and weigh down the agent appropriately. A Marsec Heavy Launcher Rocket with a count of 10 for example will still weigh as much as 10 rockets.

Brainsucker Pods left with a count of 0 will not hatch.


Android Resistances

By default, Androids are assigned the Human resistance values. Meaning, they will just as quickly fall unconscious to stun damage as Humans and Hybrids, causing Androids to take 100% Stun Gas and 100% Stun (Stun Grapple, Psionics) damage instead of 0% Stun Gas and 20% Stun damage as well as taking 100% Incendiary damage (IN Ammunition, Diablo Incendiary Grenade) instead of only 60%.

Note that this cannot be fixed by using modding programs such as "Apoc'd", which can be found here: http://www.strategycore.co.uk/files/apocd/, and assigning Androids to the Android Damage Modifier. The reason for this is that Androids are assigned the "X-COM Agents" role, as every soldier is (Humans as well as Hybrids). The "X-COM Agents" role however is assigned the "Human" Damage Modifier Group, which take priority over each individual damage modifier class and therefore overrides the "Android" modifier with the "Human" modifier again. S.E.L.F. units (building security) are treated as humans and will not be affected by this change, either.

Inventory Soft Lock

If you manage to open the inventory screen just as your soldier is dying, the game will softlock itself.

This can happen in Turn Based mode, if you approach a Popper who starts its reaction turn while your soldier is still walking towards it and you click the inventory button just at that very moment.

When the soldier dies just as the inventory screen is up the entire interface will be corrupted. If you hit the bottom right button, it'll return to the battlescape screen and everything will look normal again, however the game will still act as if you were in the inventory screen.

You will be unable to move your soldiers, shoot, turn, etc. and pressing any of the buttons, even the end turn button, will result in nothing happening.

There is no known work-around. If this happens you will have to restart the game.

Design flaws

X-COM Recyclotorium - Superhuman

On the Superhuman map X-COM is assigned the ownership of Recyclotorium Two.

This is most likely an oversight by the map's creator. Recyclotoriums usually are only owned by Evonet, while X-COM can only obtain ownership to base facilities.

This decreases the difficulty on Superhuman immensely; during Alien Retaliation attacks the UFOs will frequently target the Recyclotorium building instead of actual X-COM bases, completely averting any threat to the player as there is no fear of your base collapsing and possibly killing all your personnel.

The Recyclotorium can be reassigned to Evonet with modding programs such as Apoc'd.

Cannot rotate the view

Shorter aliens (Brainsuckers, eggs, multiworms, hyperworms) might be covered by taller structures, making them hard to see or tell apart. Being able to rotate the view would fix this.

Learning AI Bugs

The Learning AI is a fragile but amazingly cool feature of X-COM Apocalypse. Unfortunately it tends to easily break or not work at all with certain distributions of the game.

Why it doesn't work with digital distributions (Steam/GoG/own (il)legal Copy)

The Learning AI is dependent on the physical location of the Learning AI files on an original physical CD, as the CD is segmented into several physical sections visible with the eye. Digital distributions such as the Steam or GoG version use .iso/.bin .cue files that are directly mounted in DOSBox, hence making the important files all available on a single track without that physical separation which then prevents the Learning AI from functioning. The Learning AI files (EXPERIEN.DAT, BRAIN.DAT, WEAPEXP.DAT) will still update and adjust themselves according to your tactics (this counts for all distributions/localizations), however the Learning AI will fail to activate and make use of it. The same counts for mounting the file on a virtual drive and using that with DOSBox.

Burning the .iso/.bin .cue files onto a CD will also not make it work, as the tracks will not be in the exact same location / read order the AI requires them to be in. This also means that certain official CD distributions of X-COM Apocalypse, such as certain localizations/versions/re-releases, also have the issue of the tracks being in an order that completely breaks the Learning AI.

Additionally, only direct CD clones of the original CD with identical burn marks on the backside of the CD will have a working Learning AI. Self created .iso files (from a CD with working AI) or other burning methods other than a 1:1 clone will again result in a broken Learning AI.

Confirmed functioning Learning AI

Currently only 2 UK versions are confirmed to have a working Learning AI, these 2 versions carry following serial numbers:

UK Original Release: MP191 207 D01R

UK Powerplus Release: PP191 207D01R

Fortunately, those serial numbers appear quite often on second hand sales, as they were the main version distributed in Europe in countries without their own localization, and will always work through DOSBox, as long as you own a CD/DVD Drive and have it mounted in DOSBox. The serial numbers are clearly visible in big letters on the CD itself.

Additionally, the 1.03 North American version is said to also have a fully working Learning AI, unfortunately there are no more details like a serial number or actual confirmation of a working Learning AI about this version, as that version is relatively hard to find.

What breaks the AI

1. Stun raids

They will scramble the data created in the WEAPEXP.DAT file.

2. Savegame loading / editing

Breaks the Learning AI by jumping values. Editing savegames, or starting a new savegame then returning to an old save will break the decision matrix, too.

Therefore, stay with one savegame and do no reloading. This also counts for when you advance in the game (had battles) but end it without saving, close the game and start it again and reload the latest savegame.

3. Any general game exploit / unintended game mechanic

In short: Play straight. No cheating, no cheesing, no reloading savegames, if you want to enjoy and experience the exciting Learning AI.

4. Virtual Drives / .iso / .bin .cue

In general, anything that is not a physical CD will prevent the Learning AI from working.

Currently there isn't enough testing done to detail what does and doesn't work. However, the Steam and GoG implementation of .iso / .bin .cue, directly mounted into DOSBox, will prevent the Learning AI from working.

5. Certain localizations / releases

Though no extensive information is available, it is assumed that the German/French/Italian/Russian/etc. localizations do not have a working AI due to the way the CD's data was written on them.

Following releases are confirmed to have a NOT working AI, due to not being 1:1 clones, causing the Learning AI files to be on different tracks than in the original release:

UK Hasbro Interactive Release 1.00: 51747.331.DL (Disc 2)

US/NA 1.00 Release (Multiworm CD Cover) (No serial number available)

6. Installing the game from any other source other than the original CD through a physical CD/DVD Drive

Yes, the AI is that fragile.

Please Insert CD Bug

The "Please Insert CD Bug" that many players suffer from on modern distributions (Steam/GoG), whenever they start a battlescape mission, is tightly tied to all this mess. It too is dependent on a physical CD and will not occur on official distributions as long as they are played with the original CD on a physical CD/DVD drive.

The main reason for that happening with the Steam/GoG version is because both those versions use the minimal installation setting on top of having the image file directly mounted via DOSBox, as well as the data from the mounted image files being read too fast.


The "Please Insert CD Bug" cannot be completely mitigated, however you can cut down the frequency at which this happens:


Simply copy the "XCOM3" folder from the "CD/.iso/.bin .cue" onto your PC.

(whereever you have designated C:\ to be for DOSBox i.e. C:\Games\DOSBox\Games\"HERE")

Then rename the folder to "XCOMA" and then do a fresh install (200 MB optimal installation) on top of the folder.

That way, even with a virtual drive / image file, the error message won't occur as often anymore.


However, keep in mind that you should still save before starting ANY battlescape mission, i.e. UFO Recoveries, Investigations and Raids. As this mitigation will only lower the frequency of that bug but not completely remove it, you do not want to lose an hour or two of progress.


Also, directly mounting image files into DOSBox is not a good idea, as the integrated mounting system for image files is horrible and can lead to errors during gameplay.

Instead just mount the image file with Windows and then mount the assigned CD Drive as cdrom in DOSBox, as example:

mount d f:\ -t cdrom -usecd NUMBER

"F:\" being the drive Windows 10 assignes the mounted image file.


(to find out what number to put into "NUMBER", type "mount -cd" into DOSBox and then enter the number that is shown left from the drive. I.e. 0. E:\ 1. F:\, in this case it should be "-usecd 1". DOSBox has to be started AFTER you have mounted the image file with Windows for it to show its drive letter.)


Funky installation / UFO2P.exe TAC2P.exe and UFO2P4.exe TAC2P4.exe

When installing Apocalypse the installed UFO2P.exe and TAC2P.exe files inside the UFOEXE and TACEXE folders are not the actual UFO2P.exe and TAC2P.exe files. Instead, the installation takes the UFO2P4.exe TAC2P4.exe files and renames them to UFO2P.exe and TAC2P.exe to be used instead.

The UFO2P.exe and TAC2P.exe files were designed for 486 computers with less performance and processing power while the UFO2P4.exe and TAC2P4.exe were designed for the newer Pentium processors.

The direct differences between these files are not known to me, however mixing them up can cause weird errors to happen in the game. (one example is the current GoG Galaxy installation where this exactly happens)


All modding programmes (like Apoc'd) as well as most game mechanics and formulas discovered are taken from the renamed UFO2P4.exe and TAC2P4.exe files. Therefore using Apoc'd on the original UFO2P.exe and TAC2P.exe files will cause errors and weird bugs.


To prevent any weird installation behaviours it is recommended to simply copy the XCOM3 folder from the CD over to your games directory, rename the folder to XCOMA and then doing a fresh full installation on top of that. Optionally, also copy the "music" file from the CD over to where the XCOMA folder is located (not inside of it).