Hello, the issue I'm dealing with has been happening for a couple of months already. I keep seeing chunks, that are cut off on every single world I start playing, but this only occurs after closing the game. Basically, I can start a new world and everything will be normal, like nothing is wrong, but as soon as I save, close my game and start the game and world again, chunks that weren't discovered yet get cut off (even while not using the same names for saves). In vanilla Minecraft (1.17,1.16,1.15,1.14) it's often seen on trees, that get cut in half and rivers, where the sand, clay and dirt change, but in modded Minecraft it's more drastic with whole Biomes changing after 1 block. The land borders always stay the same, so this issue doesn't occur in oceans. It also doesn't cut off structures.

I also deleted and reinstalled Minecraft, as well as Java, but it doesn't seem to change anything.