When playing a t4 Lightless arbor in multiplayer, opened by my key while the party leader did not have t4 unlocked yet, the Mountain Beneath froze and stopped attacking while we were burning the Kindling. It is now stuck in place and not opening the door to stage 2.
The boss is stuck
here’s my Log File.
Update: The boss froze on t3 with the host’s key as well.
Update 2 We determined that the cause of the freeze was Blind on hit, I don’t know if this can be reproduced by all sources of blind or not.