This has been going on for about two weeks, stuff will randomly disappear and I cant figure out why. The first time it happened I went into the nether and left after walking about five blocks away and saving and quitting. When I logged back in, the portal was gone. I also lost a few random items out of chests, sometimes even stuff I hadn't used that day. Today, part of a powered rail thing I had made disappeared, something that I had built a few days ago, and this time it disappeared after I left Minecraft on for about an hour because I had to leave and do some stuff. My screensaver was on, but after returning to my house a large portion of the rails were gone. This very annoying and I have already tried uninstalling/reinstalling it. Does anyone have any idea why this could be happening or how to make it stop?