I'm running Multiworld 1.4.1 for forge 1.18.2 on a self-hosted server with a custom modpack and world.
When I first added the mod I created a test world to make sure it works, which went fine. I then tried to copy-paste the files over to create a duplicate world, which, on restart did nothing. At this point the command itself broke and none of the commands except for /mw tp and /mw list functioned. All the other commands had no results. The issue persisted after several restarts and one reinstall of the mod, and also seems to be persisting clientside in a fresh singleplayer test world.

This is the output upon creation of a new Multiworld:

Details:
Multiworld Forge v1.4.1
Clientside & Serverside issues
Forge v40.2.10
Minecraft v1.18.2
Custom modpack & Custom world

Also, there is no config for the mod that I can find, which could help fix the above issue.

More information likely available by request