I haven't had much time to do more testing, but it seems that WorldUtils.getWorld attempts to get the client world when it should be getting the server world - I found it when getting disconnected while trying to set the outputs of a vacuum hopper on a server. I made a temporary fix for the server only (just remove the conditional and always get the server world) but I figured you should know about it.

Here's the stack trace from the server after trying to assign a vacuum hopper output.

This function was supposed to handle both client and servers, but wasn't reliable enough.

Thanks!