I had started a world, played on it for like 3-4 days straight, then while I was mining, the blocks behind me after i got out of render distance appeared back and destroyed all the torches I had placed like I was never there. Then the game froze and force quit itself. When I logged back in, the world had deleted itself, so i created a new world, recorded a video of me playing on it, finished the video, and then the game froze again and deleted the world again. I am playing in single player worlds.