1. find a friendly or unlocked Prowler Utility
2. open its cargo belly
3. on either side of the cargo grid, stack 2x 2SCU containers on top of each other
4. now, tractor the UPPER container (that would technically be the lower one directly snapped to the grid)

What happened
the container snapped on top of the lowest container (the latter being the one you just tractored) suddenly poofes in sparks and smoke, never to be found again

What should have happened
the container snapped to the container that was tractored should have fallen to the ground below the cargo grid

OR

I should not have been able to tractor the container snapped to the grid while another container is snapped to that container