UFO: Alien Invasion 2.3 IA-32 Oct 22 2010 Linux DEBUG
I don't think this is a known issue, my search has only found vaguely similar claims in old bug reports where the users did not cooperate with the devs...
I have encountered this bug numerous times before in this version. I remember some details, and will try to produce a save file.
It is a save/load bug. Save the game while your dropship is en route to a mission. When you load that save, you will rarely see this bug. I have never encountered the bug with no dropship en route to a mission -- but then I don't typically leave missions unattended, so it might appear regardless.
What happens:
This is an all-or-nothing bug. It applies to every mission, every nation and every dropship en route to a mission, or to none at all.
All dropships en route to missions change their orders to return to base.
Happiness decreases in nations due to all(?) unresolved missions.
If happiness decreases due to an old mission, without the game being save-loaded, nothing out of the ordinary happens. I'm going to try and see what happens if I save exactly when happiness is due to decrease. (EDIT: Nothing)
Terror missions disappear from the geoscape entirely.
If you let the clock run for a little while, terror missions will reappear. When this happens, the player is informed of a new mission.
I did not pay attention to whether notification for a new mission is also shown for crashed ufos. (Immediately upon loading, as they don't disappear.)
The bug is deterministic. It always appears when a particular save file is loaded, or it never does.
The bug does not seem to appear in a save file when the clock is stopped and the game repeatedly saved/loaded.
The bug does not seem to appear in a save file when the clock is set to 5s and the game saved/loaded in quick succession.
If you save the game and continue playing, nothing out of the ordinary happens even if that save file will manifest the bug.
EDIT: Looks like I'll have to play the game for some weeks to get the problem again. I just don't have any of the saves anymore. Hasn't anyone else seen this?