This game crashes whenever one tries to move a character who has become imobile. Often, it is due to a spell lowering the characters' capabilities and, while there are signs that this has happened, it is easily not noticed. It's a known bug but one that Larian has not fixed. I'm sure they're just too busy with much newer games but, since your (GOG's) fortee is older games and you sell it, it may well be in your best interests to fix this extraordinarily frustrating glitch. Please!