I've seen a weird behavior where the Alien can take reaction shots even though they are out of range of their victim.
I now have a save game (with mods, unfortunately) where the alien placed at 19 east, 7 south shot at my advancing scout. From the player's standpoint, that tile is still black, out of range.
I've tested with debug mode : The alien doesn't "see" the soldier, according to the UI (no [1] sign). Yet during its own turn, the alien AI keeps staying on this tile on shooting at my soldier.
Anybody has an idea how to troubleshoot better ?