Doors push you into the ground.

When going though a door, if you walk at in a certain way whilst closing it, it will make you stuck. If you open/close the door to try to get yourself unstuck, I think the game registers the 2 halves of the door as different blocks in a way that it ends up pushing the player go into the swimming animation and get stuck in the ground. The game was also having some performance issues before hand and there was lag when the game was registering when a block was destroyed/placed.