As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ODOR SIMILAR TO DIRTY SOCKS NOTED IN AFT CABIN AFTER TAKE OFF. DISSIPATED AFTER FOLLOW QRH PROCEDURE TURNING PACK #2 OFF. FUMES RETURNED DESCENDING THROUGH 6000. SELECTING FLAPS 1, ODOR RETURNED AND COULD BE SMELLED IN CABIN AND COCKPIT. MAINTENANCE FOUND BOTH RECIRCULATION FILTERS DIRTY AND REPLACED THEM PER AMM 21-51-41.