I attached a text file containing the development console. I spawned a few chunks away and I walked to the chunk that was broken. I broke 4 blocks, saved and quit, and opened the world. Hopefully, this will help you fix the glitch. Let me know if you need anything else. Thanks so much for helping me out!
This happened to me too. Scared me a bit.
I've been doing a bit of experimenting and found that it's only when I quit the world that this happens. It reverts all blocks, mobs, everything to how it used to be.
Also, it's near coordinates -921, 72, -283. It's chunk 7 8 5 in -58 4 -18
Hopefully that helps.
No. Only the blocks and mobs around that chunk do this.
I can confirm that I have the same problem in my survival world.