As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DESCENDING THROUGH 18000 FT FLIGHT CREW REPORTED A STRONG MUSTY DIRTY SOCK FUMES, CONTINUED TO LANDING. MAINTENANCE FOUND OIL LEAKING OUT OF THE APU FUEL CONTROL UNIT DRAIN. MAINTENANCE REPLACED THE O-RING ON THE APU FUEL CONTROL UNIT SEAL TO GEAR BOX PER AMM 49-32-11. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED.