As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EQUIPMENT COOLING: MOLDY/MUSTY/CHEMICALLY SMELL COMING FROM ALL VENTS WHILE THE APU IS RUNNING. CORRECTIVE ACTION: SEE STEP 3.2.2 ODOR DISAPPATED AFTER BURN OUT, NOTIFIED MCC AND AGREED TO SIGN OFF ODOR AND PLACE APU ON DEFERRAL DUE TO BORESCOPE RESULTS.