I opened up my vanilla survival world a day after its creation and noticed the sun was massive. It was flickering and jumping around the sky every now and then, so I restarted my game and computer entirely. When I logged back on it was still abnormally large.

Around 30 minutes later I joined back and it was broken apart as you see in the other image attached. Now when I sleep the texture flips upside down, then the next time I sleep it's rightside up, so on so forth.

I don't have any modifications, hacked clients, nor have I ever opened the world to LAN or turned on cheats.