As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING DESCENT AT 12,000', THERE WAS A STRONG ODOR OF MUSTY DIRTY SOCKS THAT LASTED FOR 6 MINUTES. ENGINES WERE AT IDLE WHEN THE SMELL BEGAN. MAINTENANCE FOUND THE APU LOAD COMPRESSOR SEAL LEAKING OIL AND REPLACED THE APU PER TASK CARD 26L31049003.