When you open the backpack, it kicks you out of the server and gives you the following error

[ItsDester]

When you open the backpack, it kicks you out of the server and gives you the following error:

[GeorgH93]

Looks like it's caused by the Adventure library.
I don't have the time to make a workaround for this lib, so please just remove the color codes in the config file for BackpackTitleOther and BackpackTitle.

[ItsDester]

I found a solution, you can use minimessage colors