Crash when assigning config to world

Whenever I assign a config to a world, the server (1.21.5 paper) crashes. Prior to doing so, the configs are also not generating anything. I tried as well with the example air config.

crash-2025-06-25_04.05.06-server.txt

It also looks as though others are having getting the plugin to work on 1.21.5 (see here for example)

Seems like only works in spigot from 1.21.5 onwards