As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ON CLIMB AND DESCENT WHEN GOING THROUGH MOISTURE THERE WAS A MUSTY SMELL THROUGHOUT THE CABIN. MAINTENANCE IDENTIFIED AIR OIL COOLER TUBE LEAKING OIL. REPLACED APU OIL COOLING FAN O-RING AND ACCOMPLISHED A SATISFACTORY LEAK / OPERATIONAL CHECK PER AMM 49-52-51.