Varhesh (Terrace Boss) stuck in center pillar during phase transition

I play a crit wander with cold damage and knockback on crit mastery
During the first phase transistion this boss is stuck in the center pillar and the phase does not progress, that is snow balls come out of the pools, but no reflections spawn
Tp out&in did not help
I am therefore stuck in the boss room and cannot complete nor continue the map