When I tried to generate new chunks near existing ones on my server, minecraft kept crashing. When I generate new chunks separately from the old ones, there's no crashes. Chunks were also on top of each other, floating shipwrecks appeared, and there was ocean below existing terrain. Then i tried to open this world in singleplayer (not on the fabric server) same crash occured. This world is very old, it has chunks from 1.13.2, but these ones are recent (on screenshots and world file). 

I've attached 2 region files what lead to the crash below (they are not the only ones affected)

How to reproduce

1. Open attached world file
2. Tp to 500 ~ 0
3. Wait for the crash