https://github.com/SE7-KN8/wool/blob/1a570b136d62eaf87110aee1b4ff4fffa67f7259/src/main/java/com/github/se7_kn8/wool/Wool.java#L129

This mod crashes at load on the dedicated server, because you're referring to the ClientSidePacketRegistry in the common initialize. Move create a client initializer and move client side registration there to fix it.

Thanks for the information, I will publish a new version to curse ASAP.

Update: The new version is available.