As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANTS REPORT MILD MUSTY SMELL COMING FROM ROWS 4 AND 5 IN CABIN. MOST NOTICEABLE DURING CLIMB AND DURING CRUISE WAS IT WAS EXTREMELY FAINT. MAINTENANCE REPLACED BOTH RECIRCULATION FAN FILTERS PER AMM 21-21-41.