In the survival mode I randomly get hit with something when I stand on certain blocks. It happens at random blocks, and when it does there are no enemies near by causing it. Might want to see into that.
That happens to me as well. I'm inside the house and for some reason I get attacked by pumpkin heads from the outside. There are no holes to the walls, so I cannot see a way as to how I can take any damage...
The distance between Zombies, Wall and Player is one block (actually wall)!
If there are two blocks that are close by and only contact angles, and the player stands between the angles, and the zombies stand on the other side, so then the distance between the player and zombies will be less than one block and Zombies can hit the player!