As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAKEOFF, CABIN CREW NOTIFIED FLIGHT CREW OF A BURNING ODOR IN THE CABIN. FLIGHT CREW THEN PERFORMED AN UNEVENTFUL AIR TURN BACK. ON INSPECTION, MAINTENANCE FOUND OIL IN THE APU BLEED DUCT. MAINTENANCE PERFORMED A DUCT BURN OUT AND RETURNED THE AIRCRAFT TO SERVICE.