Multiple Deluxe Gear Boxes
That is not a bug. There are several different one of the various champion boxes with the same name an rarity. For example there are around 7 different exotic gilded strongboxes.
Each family of mobs gives their own boxes/bags/etc. So you can have a few different stacks of exotic ones, or rare ones, or any other tier. The wiki will show you all the different ones. =)