When you try to pick up and item from a floored bag or directly from the floor/wardrobe/anywhere not in your inventory as far as ive seen and try to combine them directly like 2 canisters for example the one you dragged the item onto that was in your bag already disappears and is replaced by the one you dragged over it. This has happened every time so far and is repeatable it happens for magazines and other items too so its universal.