When it happened to me a few days ago on a week old world I thought it was related to a hardcore mode addon I installed. I deleted it, restarted my world on the same seed and rebuilt things to where I had them in creative then started finishing my starter base. It saved multiple times that day, no issues at all I played built my base gathered resourced locally, dug down to diamond level under my build. No issue until I checked something in my creative world came back to move some lanterns and immediately noticed the lag and ram spike and then my world crashed. My world never crashed on the original problem it just didn't load certain areas around my base. In this new version I haven't ever loaded those chunks. I just teleported the 14,000 blocks to where I decided to build my stuff.
I loaded 1 of my 4 backups that I just created after my previous save and it pretty much crashed before it built the world. The files that crashed are all around 16MB now but the 1 world I haven't loaded back up yet is at 65MB if that gives any clues. Both times quitting and going to a creative world quickly quitting again and coming back to my survival world caused this issue for me. If uploading any of this data could help point me in that direction I don't really know what I'm doing. I'm on the windows 10 version. I appreciate reading everyone's updates and thoughts on this.
Had this happen to me since yesterday after a lot of work on a new survival world. Had a back up and loaded that today made a lot of progress for some hours then this issue happened again just now this time crashing the game completely. before I could walk up to unloaded chunks and just stand there. Do I delete these worlds? I only have 2 saves left I don't even want to load them up right now because of this issue I'm in windows 10.
I seem to have it when I quit and load a creative world and swap back and forth to try to replicate a build.
Just a heads up to anyone following this thread they just pushed 1.18.31 out that addresses this bug plus a few others. I loaded up my world and played around a bit and it does seem to have been solved at least for me. Thank you Devs appreciate your hard work.