Game crashed when I played a coop mission for a while already.
Mission: co40 Domination! Blufor [3.99q]HUD 0.1
Server: HUD Arma3 DK #1 Domination
The last thing I did was flying a chopper I got from a sidemission with some AIs inside and one AI left somewhere on the ground since it didn't move.
It is a pitty that this game still has such issues years after its release.
Previously it was already crashing multiple times on a friend's computer (some other bug). Registering here and filing the bug report is a big barrier. I bet most crashes/bugs never get fixed because nobody reports them. A game with this price should come with less (fatal) bugs and an automated way to collect crash reports!