Same issue. It has happened twice to me.
From what I gather something is bugging out on either your mc or one of the companions. I'm pretty sure it's something to do with location and the game not correctly being able to tell where that character is. If the character who is bugged is kept out of combat, combat can continue normally. If that person is in combat the AI will take no actions. Presumably it is trying to calculate actions and bugging out on whichever character is having the problem. This eventually times out and causes them to skip their turn.
This first happened to me with Astarion, and leaving him in camp allowed me to continue the game. I am unclear when precisely this happened with him.
However, it has now happened mid-fight to me with Gale against the Bulette. It downed him on the edge of a ledge (climbable) and when I healed him and he stood back up the bug occurred (in the rest of that fight, and in other fights moving forward). I'm pretty sure the game couldn't figure out whether he was on the ledge, or off of it.
The other thing this bug does is cause that character to bug out when following you across jumps or climbs. Again, I would assume this is because the game is trying to calculate where that character is and failing. You can get the character to jump/climb but you have to switch to them and do it manually.
Sometimes my previous saves work and sometimes they haven't. Not sure what causes that or why. Edit: Reloaded the same save right before a fight like 8 times. 50/50 split on whether it works or not.
Last edited by StoicNomad; 19/10/21 06:25 AM.