Seconded! I had to roll our server back to 20w08a because of this issue.
This bug also removed our banlist. Potentially game-breaking for a server!
This may also be an issue because the 20w09a snapshot keeps erasing OP permissions. In our server world I had to keep op-ing people when the game would remove it.
Benjamin Poulsen
Seconded! I had to roll our server back to 20w08a because of this issue.