Originally Posted by PeteNewell
If I click and drag too often, I routinely pick up another item on my drag path.

This. If I have my inventory open on the left side of the screen, and open up my backpack on the right side of the screen, I run into this scenario sometimes when moving items back and forth. I can grab an item from the left side of my inventory...and when moving it across the rest of my inventory to the backpack on the right, it will sometimes pick up another item instead (usually the last item in my path before getting out of the inventory).