When I load MCPE, a world will be selected and automatically loaded. I thought I had a corrupted world (extremely laggy and a lot of chunks not loading), so I deleted it, thinking that would solve the problem. At the time I was using a texture pack, so I reinstalled a clean version of MC with the same issue. I deleted the possibly corrupted world. It started autoloading another world. I looked on the website to see if there was a bugfix and I saw the post that 0.12.3 was out, so I installed it and tested with the same results. I always completely close (I swipe it off, not just hit home) so it shouldn't be an issue with having it loaded. I'm running on an Acer Iconia One B-750, plenty of RAM remaining, no CPU overheating, etc.
I also recently had issues with screen sync while charging, so I tested it off the charger and I still get the bug. This bug wasn't there when I first installed 0.12.0 betas and didn't start for a while after I got 0.12.1. This doesn't seem to happen when I am in Airplane Mode. Is it something with my WiFi? I have 1 external server added and 2 single player worlds. I don't know the cause of this issue.