Very peculiar bugs.
Firstly, on one battle the damage reduction was not removed after the first set of adds. We had to return and reset the battle to continue.
Secondly, upon returning, he would walk up to Cid before anyone had engaged or aggroed (or even entered the Armamentarium), start hitting Cid and then, 15s later, it would reset after locking us out with nobody inside.
Rinse, repeat.
Humorous, indeed, but obviously not working as intended. :)