When I equip a belt, and remove the belt, the armor don't reduce as expected.
Quit the server and rejoin (or quit singleplayer and reopen the map) reset the armor to the expected value.

MC: 1.18.2
Forge: 40.1.16
Malum: 1.3.6
OrtusLib: 1.0
Curios API (Forge): 5.0.7.0

Here's a demonstration:
https://user-images.githubusercontent.com/11332249/169175080-e701ab70-a9bb-4076-a80d-8462fafdd04b.mp4

Haha that's hillarious :)

Magebane belt: