I decided to fight the ender dragon multiple times and after autosaving the game froze and crashed I then proceeded to kill ender dragon again and after 2 or 3 fights the same occurred and reset to the first fight. I then proceeded to work on making a nether hub and after returning to the over world for supplies the game attempts to auto save and proceeds to crash. I have been able to replicate this about 3 or 4 times and even spreading the intervals at which I leave the nether apart. I have a recording of the event of leaving nether and crashing but file size is 18MB, exceeding the 10MB limit. When I went more than a couple chunks past what was loaded immediately around the nether portal the game will crash again and Im able to replicate multiple times. Now when loading world I start to see items in my hands then the first chunk loads very slow  in front of me and then the world became extremely lagish as it loads about 4 or 5 more chunks in front of me. In the time it takes to load the chunks I can turn slightly then the game freezes and crashes.