All these occurred on Normal difficulty.

First bug occurred when got boss to 1/2 health and the Alpha Pariah ran into the room.  The doors did not shut behind her and the animation did not progress requiring me to Alt-F4 out of the game (pressing space bar/escape did nothing) - this was fixed by the restart.

Second bug occurred when I died during the fight.  I respawned outside the battle area and could not get back in as the doors were shut - I had to restart the level.  I did not die again so unsure if this was an isolated incident.

Third bug occurred after the fight when my Inquisitor got back to base.  The camera centered on my pet (flying cherub thing) instead of my character.  This was fixed by chatting to the quest NPC.