When wearing an chestplate and then switching the  chestplate with an elytra (In quick wearing) meaning putting it on while running, you can also switch back to the chestplate, either way then you can't take off your chestplate or elytra in your inventory. It also affects helmets when switching the helmet with another helmet while running.Idk if it's also on other platforms, but someone can change it to multiple if they want to i only work on android...