That old sentinel though (bug)

So twice now I’ve been on the old sentinel and he just sort of breaks at the second healing phase. I’ve done this level quite a bit and this hasn’t happened except today. Anyone else have this problem?

The last time I beat Saboteur the boss at the end ended up stuck for several minutes, walking back and forth and growling in the face of one player but invincible like he was in his shield / spawning minions phase. We had two Rath (I was Attikus) and I think they managed to knock him into the air right as he was going to drop into the shield phase the second time. We just sat there watching him, finally I ran up and used leap and hedronic arc on him and eventually he started taking damage again so we won.

Oh yeah probably should have pointed out he was immune lol

Just happened to me few minutes ago. Very annoying.