How did you plan things out with the duergar in advance? I schemed with Elder Brithvar to betray Nere, and when the time came followed through so he and his duergar fought with me against his.
BUT right near the end of the fight one of Brithvar's clerics decided to cast a big dome of silence over the central platform that just stayed up after the fight (not sure if she was still concentrating or if this is a bug too). And because Brithvar couldn't speak in the usual location of the autotriggered cutscene after Nere's death, the quest just got stuck. I did manage to catch him when he briefly popped out of the silence dome but talking to him then didn't trigger the same dialogue choices to either get him to free the gnomes peacefully, let him go with them or fight to free him that would move the quest on.
I ended up doing the whole blooming fight again, and was not impressed!
I seem to recall having a similar issue in a previous patch when I'd sided with Brithvar and he'd got shoved into lava, and I'm not sure if that is fixed either.
