As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ALL PHASES OF FLIGHT WAS A BAD MUSTY SOCK ODOR IN THE CABIN. INSPECTED RECIR FAN FILTER, FILTER WAS VERY DIRTY. R & R RECIRCULATION FAN FILTER. IAW AMM TASKS 21-22-22-000-801, 21-22-22-400-801. OP'S CHECK GOOD. NO ODOR DETECTED, NO OTHER DECFECTS NOTED. RETURNED TO SERVICE.