As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OIL LIKE ODOR DETECTED IN REAR CABIN AREA. THE ODOR WAS NOT STRONG OR PUNGENT, BUT IT DID SET OFF THE AFT LAV SMOKE DETECTORS. *S/D* THE APU WAS REPLACED DUE TO CONTAMINATED PNEUMATICS. DURING DISASSEMBLY AND SHOP INSPECTION OF THE APU A PLASTIC BAG WAS FOUND IN THE INLET.