I was processing a bunch of Agerian Armor, and looking through my inventory while one failed over and over. I flipped to my pearl inventory and then it succeeded, with the next item in queue being my Valkyrie Treant Camo. I quickly canceled the processing.

I tried to recreate the bug, and was successful by having my pearl inventory open when the autoprocessing chooses its’ next target.
It seems to pick a random cosmetic item from the Pearl Inventory to process. I don’t know if it will actually succeed, as I didn’t let it finish.