There's a bug, if you have an old world at version 1.12.2 and load it in mc 1.15.1, everything is fine until you go to x=1008 y=* z=* where the chunks won't get even loaded, also commands aren't working if you've entered this area once, and even the Show Chunk Boundarys Debug mode won't work in this area.

To see every strange thing i noticed so far, have a look at the video.

P.S: Another strange Thing: The Game doesn't get finish with saving the world, if you've entered the area once     edit: I let the game saving for ~30 min. now and it's still not finished, need to close it with sending SIGTERM

P.P.S: excuse my bad english, im originally german

P.P.P.S: Credits to Elysium Fire, I used the map Novigrad in the video