I'm playing Underrail version 1.0.1.10 from GOG.
I was getting towards the end of the mission. I was on the very bottom floor where you meet the old man being held hostage by two raiders that were waiting on a third partner.
I have a save right outside the bosses room filled with a few hostages. My strategy was throwing a cocktail right on top of the boss, burning all three raiders inside. Whenever the last raider dies, the game crashes for me. Ive killed the last raider by fire, grenade, gunshots. Doesnt matter what i use it crashes when they die.
I wanted to finish that little part of the mission but i had to skip it instead and just leave with the key.