Delve Beast Burrow Boss Bug

Hi there, im playing zerphi's last breath poet's pen vd character and deept 367 Beast Burrow chest i was going. I kill coming bears and almost summoned boss i use x3 times frost wall supported with spell cascade + faster casting. Boss was stuck on walls and boss's hp bar is gona and he become immortal but doesnt deal damage too i trought flare and go dark side with 2 flare and back boss was on ground dead but chest still not opening.

reference number : 4.185.240.007.