I recently downloaded the Version 2.34, Introducing the Caves & Cliffs: Part II update. I converted my best world to the new version. The first time I opened my world it ran for about 5 minutes until it randomly said I have no storage, which I had a lot of. My storage bar on Minecraft isn't even half way full. Upon opening my world again, all of the textures were gone. There were pink and black squares everywhere, and then the game crashed. I couldn't open the world, so I restarted the game. When I opened my world again it said "Could not open world" and deleted the world, and it's file without even asking. That was my best world, with over 1500 hours put towards it. I didn't even get to see the update before it completely caused my world to get deleted. I'm sure I can't get my world back, which is absolutely killing me, but please figure out what this was so I can think about playing the game again.