I have this error: https://hastebin.com/nelowihuge.yaml, This is traced back into LWC because the plugin was trying to get the player's groups
which then goes into the vault handler, which it seems PowerRanks does not provide correctly.

Thanks for reporting this issue.

The problem has to do with a casting issue.
This has been fixed in commit 4b5525d
It will be available in the next release of PowerRanks (v1.9.3)

This issue will be closed when the new version is released.

New version (v1.9.3) is available on spigotmc