[POE2] Rathbreaker invulnerable

Hey, so if I initiate combat with Rathbreaker, and run down from that platform, boss coming after me and soon as reach the bottom of the ramp it's immediately go back and regen to 100% HP, after that point whatever I do it's stays on 100% HP.

Has just happened to me, too. Hyenas are spawning, but the boss is idle and invulnerable, even after his armor is fully broken.

Same thing just happened to me. Rathbreaker just stands there regenerating any hits fully. He's locked in place. Nothing happens.

I've got an invulnerable Black Crow boss , wont move from his spot and been hitting him for an hours with my 15 sniper minions. He never got to the bell phase. Stuck in phase 2.