Have anybody dealt with invisible alien? I believe I met them twice already. I have not any logs or screenshots as proof however... They are shooting your soldiers but you can't see them, so you can't shoot them or figure out what going on. First time (big mansion map) i have lost battle, second (military convoy) - my soldier killed alien on reaction fire (so he could see?).
I wasn't using IR-googles then, maybe it could help...