This explains the trapjaw crash I was having. Trapjaws in narrow passages will sometimes crash the game for unknown reasons. I expect this has to do with their ability, if they jump backwards into a wall there may be something that can happen with causes this. While this may be an issue with the new movement code, I expect this could have been a bug which has always existed, but which was only discovered recently since trapjaws in the missions have only been outside where there's tons of open space.