Percussive Maintenance is a term used when a robot frees up a broken drive or weapon of either itself or its opponent while in a match. This usually happens by ripping off a part that was hindering the drive or weapon or delivering a hit hard enough to knock something back into place.
Although not counted against a robot in judging this can obviously have the potential to turn the tides of a match if the robot entered broken and suddenly is now fully functional it could very well have better reach or drive allowing it to dominate the rest of the fight.