I had a world the other day. I had not been on for awhile, so I did what any other Minecraft player would do and created a new world. The world was fine for about 1 and a half hours and my friend joins on the xbox one and it crashes but I forgot to save before quitting so it never saved. Here's the problem, I Then created a whole new world and like everything else it was all fine, however I had another friend log on an android Pocket Edition and the world started making a border even though it was infinite, but I made a copy of the world and I was the only one on yet it still does it and your pets or horses will glitch through and glitched until they suffocate or you close and restart. It seems to happen whenever you go exploring it will cut the border despite it being infinite