Version Info

• Minecraft, 1.12.2
• Core Lib, 1.1.12

Steps to Reproduce

• Joining a server without the "MovingElevator" server mods
• Open creative tab
• Switch page
• Crash game ....

Crash report (~/logs/latest.log)
crash-2023-10-23_18.02.43-client.txt

Moving Elevators is required on both the server and the client. You should not be able to join a server without Moving Elevators with a client with Moving Elevators.
If you can, that is likely caused by some other mod you have installed.

Okay, I've got two servers 1 with the mod and the other without.
Thanks just the same, I'll install it on both servers.