I’m assuming the issues you refer to are in level 2? If so, it’s supposed to get stuck on that platform. If you look closely, there is a trap door that closes when you press the button, and that trap door doesn’t close in time for the gravestone to fall through. The solution to the puzzle is to die in a room just below the button, so that the gravestone spawns without the trapdoor being activated. I think there is a screenshot I posted somewhere in the comments showing where you’re supposed to die. Sorry if that puzzle wasn’t more clear.
As for the falling through the middle of the gravestones, I have seen that glitch before, but I’m not really sure how to fix it yet. I will look into it though! :)