While testing what happens when using dispensers to equip Piglin with different items, I used them to equip shields. I killed the adult piglin to reset for a video when I noticed it dropped 2 shields. I also tried this with baby Piglin with the same result.

First 2 kills were with the new Netherite sword. I also tried all other swords with carbon copy results.

Out of all types of armor, weapons and tools equipable by dispinser, the shield is the only one I've noticed duplication.