As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO DEPARTURE DUE TO AN ACID ODOR AND HAZE IN THE CABIN AFTER TAKEOFF. BOTH AFT LAVATORY SMOKE DETECTORS SOUNDED. MAINTENANCE FOUND THE APU OIL CAP NOT SECURE. THE APU WAS REPLACED AND WC 2120-2368 COMPLETED. THE RT ACM WAS ALSO REPLACED BECAUSE OF AN OIL LEAK. MAINTENANCE PERFORMED A DUCT BURNOUT AND REPLACED THE COALESCER BAGS. THE AIRCRAFT WAS RETURNED TO SERVICE.