I don’t think this is server.properties related because the only things I’ve changed are server-name, gamemode, difficulty, allow-cheats, max-players, and level-name. If I replace the server-properties, it won’t load the world, it will generate a new world. Are you asking me to see if the issue occurs with a new world instead?
There are no addons installed
Reproduction steps are:
Run version 1.21.80.3
Be forced to update server to 1.21.90.4 because the client updated
Observe error in log on server startup
Here’s the world files.
https://drive.google.com/file/d/1SflWYrud-H8ZKgd4kFyHvABzONBTgNzL/view?usp=drive_link