ZernoK

Having sort of the same issue, x2 medium/big drones standing next to each other in a base defense mission and killing either of them will crash the game. Also the drones will not move at all during the mission. http://imgur.com/ITcli6o Savefile if needed. https://www.dropbox.com/s/flxl4km9bjgke46/AutosaveIM2014-01-22_21.15.03.sav

All my games are on automatic updates, so that is not the problem.

Reinstalled the game, seems to have fixed it for me.

I am having the same issue. No aggression, only reaction firing at my troops from cover. Only aggression I see is on terror missions, and then I'm pretty much just sitting around my dropship the entire mission. The aliens also knows every where all my soldiers are at all times even if they don't see them. So I can manipulate the movement of the aliens somewhat as they try to get to a better cover/position according to my soldier that is closest to them, even if they haven't seen my soldier at all. Meaning they become sniper food pretty often. Most noticable against camping alien in hangars on base defense missions. Been playing the game on Steam.