That is the error log

debug.log

For a temporary fix, you may try to delete the file named ExtShapeClient from the mod's jar.
I'll release a fixed version in a few days.

It is so strange that I've tested it in my environment of development and the dedicated server can correctly start.

For a temporary fix, you may try to delete the file named ExtShapeClient from the mod's jar.
I'll release a fixed version in a few days.

Thanks, removing the class file fixed the issue for now.