I also encountered one of the enchanted pickaxes that I had in a chest changing to have the three enchantments become Protection V, Protection III, and Protection III... Screenshot attached
ah OK, that makes sense, sorry about the extraneous bug then 🙂
I also just encountered this bug in 17w46a
I also encountered one of the enchanted pickaxes that I had in a chest changing to have the three enchantments become Protection V, Protection III, and Protection III... Screenshot attached