Can get stuck in pit in Cassie's mind
At the start of the "Deep inside Teacher's Domain" section, it's possible to land and get a respawn point set on several of the books in the pit. There's no way to climb back out and you are forced to exit and re-enter the brain. This also resets your progress to before the book transition if playing through the level for the first time.
In addition, although I've been unable to recreate it, I somehow managed to survive a fall into the same pit on one occasion by using the levitation bubble. I hit the bottom without dying and was stuck in a solid black area I was able to travers around. Using the Pyrokinesis bubble to see the walls I walked around trying to find my way out and somehow ended up clipping outside of the geometry completely.
I was not recording for the initiation of the glitch, but do have a recording of the infinite falling as proof. https://youtu.be/2gUOPPJEimU
I fell for about 5 minutes before it finally respawned me back at the same checkpoint before the book transition to this part of the level, and all of the figments I have previously collected in this segment had reappeared.