I started a server for my family a few months ago. Today we decided to fight the dragon and look for elytra. In our search for a stonghold, we started coming across a lot of chunk borders as shear cliffs. The eye of ender brought us to a place that when we dug down, we found less than half a library... After a bunch of fiddling, my brother noticed the seed was not what it used to be. I set the servers world seed in the server properties file, deleted the affected chunks, and loaded the server again. The same chunk borders were there but any blocks broken in the deleted chunks were restored to new chunk condition. In setting, the seed remained incorrect for the initial world seed.