Game crashes, weird structures and missing horses

Hello,

Recently, Minecraft has been crashing more than expected (30 to 60 minutes after playing.

Specially when I alt+tab to other programs, the game minimizes, pausing the game. (the game is in fullscreen) When I open the game again, there is a change of these things happening:

• The game crashes while loading

• I start playing but 10 seconds after loading, it crashes

• If I move more than ~50 blocks from the loading point, the game crashes

• If I see a weird generated structure (that is not supposedto be there), the game crashes aprox. 30 seconds later (image attached)*

• When riding a horse and the game crashes, the horse disappears in the next load**

*The image attached of the weird structure is the thumbnail of the save that unfortunally crashed before I could record it. After opening the save, the structure wasn't there anymore. That's why the image is so low quality. If you can't tell what's on it, it's basically a big "slide" made of a single line of dirt and grass, filled with grass in the wholes. I created a similar-looking structure so that you could see it better.

**About this last point: One of the times this happened, I had a bee tied with a lead and I was riding a horse. When I reloaded the game after crashing, both horse and the bee were missing, so this probably deletes all mobs that are in your loaded chunk area.