Bat form. I had a poison cloud, two flesh golems, and staff attack all blasting on the bats.

met the same bug, I have tried this twice (by reload the game), in bat form you will trapped, but in normal form the door will open. btw, I counter two more bugs, 1. the dash attack seems not work for me, 2. in some case the when entering last level of the core the game would stuck.