I'm not sure if this was a nightmare repair, but it is a good story.
In 2010, as a mentor and coach for 816, I had the pleasure of watching our robot go up in smoke during autonomous mode in one of our qualification matches. Initially, the autonomous looked routine, the robot began to move forward slowly as it always did and then drifted to it's right. Initially, it seemed like a routine 'the robot is being dumb again' moment... And then it started smoking.
I frantically hit the E-Stop and ran out of the box to the side of the field to see Pete K (FTA at the time) on the opposite side of the field with a fire extinguisher. I think I shouted something like 'No, wait!' to him, and once the match had been paused/canceled (or before by some accounts) I got on the field and opened the robot's lid to air the smoke out and found no fire.
Thankfully, since the match had been stopped, we had to wait the minimum 6 minutes to reset the field. Everyone assumed that we would take the robot back to the pits to fix whatever was wrong with it, but we found the problem fairly quickly right there on the field. Turns out one of the PWM cables going to the right side of the drivetrain shorted out and burned up most of it's insulation. Some time after we found this, our 'pitmaster' was standing on the side of the field asking what we needed to fix the robot, at which point I shouted 'PWM Cables' at him. Something like 2 minutes later he came back with a ball of PWM Cables and we rigged the robot up to run without ever leaving the field... And we won the match too. Good Times.
http://www.chiefdelphi.com/forums/at...8&d=1270046943