Act 2 - Too many weird issues to count with Halsin in act 2. Thankfully I was able to talk to him at camp, get him to go meet me at the Inn and then do the Defend The Portal thing. Then he disappeared for a while, had nothing to talk about at my camp, and the "Show on map" button for his quest didn't go anywhere. Thankfully it did resolve itself later at the end of the act, I think it might have been caused because I did the hide & seek with the cursed tiefling boy "too early" in act 2?
Early act 3 - The booby-trapped toys quest, after getting the Fist officials to realize the toys are trapped, you get a quest update to go confront the toymaker. Weirdly the only options are kill him or let him leave, not turn him in? I let him leave, he vanished and the quest never updated so I still have it.
Late act 3 - All quests related to Kithrak Voss and the Orphic hammer - I spoke to Voss at the start of act 3, then to Raphael, then Voss again. Many hours later, stole the hammer, went to meet up with Voss in the sewers. He would talk to me, but he just said "Follow me to the tap room", and then he never left the spot. Tried talking to him on all characters, going to camp, reloading, etc. etc. I think this one might have broken him because I normally have at least one summon out (celestial or elemental from Shadowheart, Wyll or Gale) and NPCs go insane if you have a summon they interpret as hostile. I was able to progress the quest but maybe this interrupted him somehow. Anyhow it would have cost me so many hours to go back to a save before that by the time I troubleshot everything that I just gave up. You can still break Orpheus free at the end and get Voss's help, but you never get the greatsword (which is a shame because Baldur's Giantslayer literally does not fucking work on the ONLY two mobs in the game that qualify for its bonus damage after the point where you receive it).