Similar to MC-16763.

I threw a Splash potion of Healing into my Zombie EXP farm, and saw one of the Zombies had dropped a Golden Chestplate with Fire Protection III and Thorns I. Every spare slot in my inventory was filled with this particular piece of armor. If I threw a Chestplate away, a new one would take its place (Of course, this only happened while I was standing on the entity). EDIT: Dropping a piece of the duplicated armor, then standing on it would also fill my inventory with the armor.

I couldn't Shift+Right click to wear the Armor; I had to equip it manually. Upon taking a single hit, the armor would break, despite showing no durability damage taken on any of the armor (pictured twice, note the loss of armor points after the Creeper explosion).

(Perhaps the Armor dropped had negative durability or dropped to 0 at the same time as being dropped? Just wild guesses.) (I also apologize for any mistakes in advance as this is my first report.)