I'm having similar issues in the goblin camp. When I freed the bear from the Worg pens he joined the fight as an ally but stopped moving and attacking after moving onto a patch of Grease that the butcher had thrown from a bottle onto the floor. I got similar results when I was fighting Priestess Gut, cast the grease spell from a scroll onto the floor and she stopped taking actions after she slipped once.
A lot of things seem to break the AI, but Grease seems to be a thing the AI struggle with dealing with specifically on my end.