The only major bug I've encountered:
After killing all the druids and tieflings in the grove I exited the area through the top of the cave Zevlor hangs out in, but Astarion got left behind. I clicked on his portate and he was in the dialog from when you first enter the swamp, the game had me make a DC 20 investigation or perception check (I can't remember which). If I passed the game fed me the dialog about noticing everything is a swamp, and whether I passed or not Astarion was dropped to 0 HP but not downed. I save scummed multiple times and always got the same thing.