As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AT GATE AIRCRAFT HAS FOUL DIRTY SOCK SMELL WITH APU BLEED ON. SMELL WENT AWAY WITH BLEED OFF AND PCA AIR ONLY ON. THE FLIGHT CREW REPORTED THAT THE ODOR WAS NOT PRESENT DURING CLIMB OR CRUISE BUT CAME BACK DURING DESCENT. MAINTENANCE FOUND THE APU WAS LEAKING OIL FROM THE LOAD COMPRESSOR DRAIN LINE AND REPLACED IT PER JOB CARD 26L31049003. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED.