While on a ladder climbing through a trapdoor on the bottom half of a block, it will warp you back to it and not let you out until you open it.
I expected to be able to just open it and close it as I needed.
What actually happened was when I closed it after moving through, it would warp me back over and over until I opened it again and moved all the way through.
Steps to reproduce:
Close a trapdoor while on a ladder above it.