When Going into an area that is 2 blocks tall while on a horse, you suffocate. This works if you go up stairs that there is only 2 blocks of air above it. This was a time when i took two screenshots very fast and in the first one i am sort of inside the block and in the second its black and im suffocating... It eventually pushes you back out and only does a half heart of damage but it is still annoying.