While testing out the new pre-release update, I decided to test out my Skyblock world. I went to my nether portal, which I have surrounded with cobblestone and a small window to hit the pigman through. see attachment I have also made a small spot that I would be able to hit them by the door which they seemed to like to go to. Well once I tried it on the update, I walked into the room and pigman were walking straight through the one block next to the door and killing me. I am not certain if this goes for other mobs, but I know that this may become a bigger issue.