206. Accidentally wire a 5 volt Axis camera to one of the 12 volt spots in the power distribution board, and then when that one gets fried (admittedly with very little smoke and smell), plug in another one to figure out what's wrong.
The programming mentors wondered why the Axis camera wasn't sending a signal to the driver's station. Then they figured it out.
(They couldn't even blame electrical, because they had done the wiring themselves.)