As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT 20,000 FT THE PSU OXY MASKS DROPPED ON THE LEFT SIDE OF CABIN. THERE WAS NO REASON FOR THEM TO HAVE DROPPED. FOUND WIRE W638K20 OF OXYGEN MASK CIRCUIT BREAKER SHORTED INTO FWD LAV PUMP 115 VOLT WIRES UNDER THE FORWARD LAVATORY. REPAIRED WIRING UNDER THE FWD LAV CABINET. CHECK-C 2-22-99 MCI.