Modpack: Enigmatica 6 (0.3.2, but noticed the same in 0.3.0)
Mod version: 1.16.4-0.1.5

Setup:

• Have in my hand a (pick)axe with durability loss.
• Have the mossy ring equiped

Steps:

• Try to mine something that takes a while (obsidian, or storage drawer with an axe)

Expected result:
Being able to mine the block

Actual result:
The progress on breaking keeps resetting as long as it's being repaired, once it's fully repaired I can break the block.

Possible solution:
Don't repair the item when it's being used.