When Recovery expires, Charm of Blood cause durability damage to my clothes.

Test Prep: Mystic Dagger with Recovery, Mystic Sickle with Immolation. Charm of Blood on me headpiece.

I did this in my crossway safe space with no enemies around.
Full repair everything, top off health before starting. My HP is 715.
As fast as you can:
Cast Immolation 1 charge until your health stops going down.
Swap to knife, cast recover 1 charge.
Swap back, cast immolation until your health stops going down again.
Look at durability on clothing - it has gone down.

Spamming one spell alone does not seem to cause any durability damage. Seems specific to something about both spells.

Something in this process, which I do a lot in combat, creates a small window when my armor takes durability from my casting. The amount of durability damage is hard to predict, sometimes 5ish, sometimes 20ish. I like to use the recovery buff as "free" hp for charm of blood but the durability damage seems to start as soon as the Recovery spell stops. Its enough durability damage that my gear will go yellow/red in a single vault run if I don't repair in the middle and im doing 12k+ per fireball so I'm not getting hit much.

More than happy to screen share, send logs or answer questions!