some region files get overwritten to default terrain when uploading to realms

When you upload a world to realms it seems to overwrite the region file where the player is located to default terrain.

I had a 1.15 void world which i joined on 1.16 and it seemed to work fine but after it was uploaded to realms the region I was located it was converted to default terrain but only for about a few hundred block and then it was back to the void with my builds that diddnt get overwritten