TwoPoint

This is still an issue in 1.16.4

Also having this issue, it's amounting a lot of lag on our server, waiting for a fix. New features aren't as important as performance, please understand our frustration. We haven't had performance like 1.12.2 in a long time. It's making multiplayer harder and harder to play on.

Also affected by hoglins in 1.16 snapshots.

If its any help try checking the properties of a few folders that might hold information on the world you lost to see if there are any previous versions.