As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FLIGHT DECK EXPERIENCED MODERATE "MOLDY SOCK" ODOR DURING IDLE POWER DESCENT INTO CLT. THE ODOR STRENGTH REDUCED IN INTENSITY WITH ENGINE N1 LEVELS WERE ABOVE 64%. ODOR WAS NOT NOTICEABLE ON GROUND DURING TAXI TO GATE OR ON APU BLEED SUPPLY. MAINTENANCE FOUND THE APU FUEL CONTROL UNIT LEAKING OIL INTERNALLY AND REPLACED IT PER AMM 49-32-11. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH ISSUES NOTED.