Chunk corruption resetting random chunks in the nether when you save/quit the world or restart the server

When we restart our server specific chunks reset in the nether

a few corrupted chunks that reset to what they originally were when we restart our server, we tested this using the same seed in SP, and the same thing happens when you save/quit the world and re join

Every time we restart the server/world the same few random chunks reset to what they were originally eg. A spawning pad resets to the original fortress, a tunnel to a base resets to the original, untouched terrain