Find a metal grate staircase (there are plenty at the docks near the airport on Stratis).
Be on top of the dock, order a unit to move to the lower section of the dock (at sea level). Be sure this location is not going to result in a "straight line" path down the staircase. I would suggest placing a ship or sub near perpendicular to the staircase, and order the unit to board.
With this unique set of commands, please note how the path selection will make the unit choose to "hop" from the staircase (as it is a no-harm fall), and become stuck as a result.