As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ODOR/FUMES IN FLIGHT DECK DIRTY SOCK SMELL ON DESCENT BETWEEN 3000-6000 FEET AND ON THE GROUND DURING TAXING IN. MAINTENANCE FOUND THE APU OIL COOLING FAN DRIVE PAD LEAKING OIL. DUE TO A BROKEN O-RING. REPLACED O-RING AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK WITH NO ODORS NOTED.