it works for single player but on a server it just craps itself and none of the backpacks work at all. this intentional? the 1.16.4 works on a server yet its just the main backpack by itself.

1.12.2
forge 14.23.5.2855
backpack 1.12.2-1.0.22.22

1.0.22.22 is outdated. use latest version