Chunks are corrupt or in the wrong place
What it looks like in your log
Chunk file at [12, -4] is in the wrong location; relocating. (Expected ChunkPos [12, -4], got ChunkPos [11, -4])
What causes it
Chunk entries inside a region file are damaged or stored at the wrong coordinates. The server skips or relocates them; players see holes or rolled-back terrain.
How to fix it
Restore the world from a backup if the area matters. If it is widespread, run a region repair tool over the world.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log