As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU AUTO SHUTDOWN WITH SMOKE IN CABIN. FOUND THREADS STRIPPED AT THE GEARBOX HOUSING OIL OUTLET PORT. THIS CONDITION LEAD TO AN EXTERNAL OILLEAK. THE OIL WAS THEN DRAWN INTO THE INLET THUS CAUSING THE SMOKE IN CABIN. BORESCOPE OF THE POWER SECTION REVEALED DIFFUSER VANE EROSION AND HOT SECTION DETERIORATION. REPLACED APU