Steps to reproduce the behavior:

1. Acquire a backpack.
2. Select it in your hotbar.
3. Right click to open the backpack.
4. Observe that...
   4a. SP: ...nothing happens.
   4b. MP: ...the server instantly crashes.

Crash Log
https://stuff.thingies.site/minecraft/logs/crash-2023-01-31_18.11.51-server.txt

Versions

• CCL: 1.16.5-4.0.7.445
• CB Multipart: 1.16.5-3.0.4.123
• ProjectRed: 1.16.5-4.13.0-beta-23

Your crash log link isn't working for me

Sorry, my router spontaneously cleared my port forwards. Should be fixed now.