Moment of vulnerability bugged in endgame

95% of map bosses in endgame are unaffected by primed for stun moment of vulnerability. The echo instantly dies and even spawns remnants as if dying. Very odd because it worked perfectly through the whole campaign.

Also, during the lord geonor fight at the west gate, if you use moment of vulnerability while he's in his small wolf form not his second phase, it completely crashes the game requiring a new waystone to be placed and map restarted