As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. FA REPORTED MUSTY ODOR MID CABIN AFT. TURNED OFF PACK 2 AND ODOR SUBSIDED. TURNED PACK 2 BACK ON AND ODOR RETURNED AND CREW TURNED PACK 2 OFF FOR REMAINDER OF FLIGHT. MAINTENANCE FOUND THE APU MAGNETIC DRAIN PLUG LEAKING AND REPLACED IT PER AMM 49-91-42.