Alexander Doubrava

@Daan Kuster The only way to fix it is by having a backup of the world or region file. If you have no backup you could try to reposition chunks manually but it is very likely that many chunks are completely missing(overwritten) in the region file. Here is an image of my world xD: https://prnt.sc/s49j2b

I have experienced the same problem on my server.

Somehow the order of the chunks in the region file gets mixed up. In the chunk itself the correct position is still stored until the chunks are loaded. Then minecraft goes like you are standing in the men's toilet queue and even though you tell me that you are a woman you have to be a man because you are standing in the men's toilet queue.
So minecraft says chunk your data is wrong you actually belong there although the chunk is actually right.

But i have no idea what happens to the chunk actually at that position in the file.