Firstly, this is under modded because I'm using optifine, no other mods are used.
I've had this file for a while now and I never had crashes with this game. Yesterday, it happened once, I re-launched minecraft, got into the save file again and it crashed, again. I, then, restarted my PC and the issue seemed to be fixed. Though my performance has decided to plummet these last few days when using VBOs so I had to turn it off and it has kinda gone back to normal.
Anyway, last night, a while after I had restarted my PC, I started using the Elytra, which I had got earlier that day, to uncover more of the world and fill in my map. After quite a bit of exploring, I could see some really weird chunk/world generation with literal squares of different biomes being smushed next to each other with different Y values each. I didn't really pay that much attention though. Then, a few minutes later, my performance and chunk loading started acting up a tiny bit and then the game crashed. Since then, I've tried to jump into the save file quite a few times, tried restarting my PC, turning VBOs on and off. The game keeps crashing constantly after about 30 seconds of entering the world causing an endless loop of me starting on the last auto-spot and the game crashing after failing to load the world as fast and the game just freezing and then crashing.
This is actually pretty frustrating since I've been playing on this save for more than a month and only yesterday decided to fight the Dragon and go get the Elytra to get around quick. I have quite a few log files but I'm not really sure how to upload them.