Hopper "regenerating" items

I open my survival inventory in creative. I place 3 stacks of 64 hoppers inside. I stand on top of a hopper. I open my inventory (NOT the hopper GUI) and put the cursor over the stacks of hoppers and press ctrl-z (z is my drop key) and drop the 3 stacks into the hopper. Then I open the hopper GUI and the 3 stacks of hoppers reappear in my inventory. This has been happening in the previous snapshots as well and has not been solved...