Modpack version
1.58

Can the issue be reproduced?
Yes

Issue
When a screen or creative screen from rftools is shift+right clicked with a crescent hammer it will duplicate into two separate screens with different NBT data (One will have a blank NBT tag while the other will be registered to the owner). This duplication only works while playing on multiplayer.

If someone else could also confirm this issue on their instance, that'd be great. Especially if you're able to reproduce in singleplayer ^^