I have just had this happen to me too. Only one member of the party got the final cutscene (and thus their quest updated). It looks like the rest of us are going to have to re-do the dungeon in story mode. Something I really can’t be bothered doing as it was such a lackluster experience the first time round – let alone a second. Any news on when this might get a fix, and whether a fix would work retroactively?