When in creative mode and trying to shift-click armor onto your character from the inventory, the armor will often times be deleted, or duplicated. The same happens when shift-clicking the armor from your armor slots, into your inventory.

How to reproduce:
1. Go into create
2. grab a set of armor
3. shift-click all the armor onto your player rapidly
4. You should see it start to flash, and some of your items get deleted
5. try the same in reverse, taking armor off by shift clicking, it will duplicate armor.

Note: You may need to test this on a realm/server, it rarely happens in single player.

I will update this post with video of this bug in action later