As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT RETURNED TO ATL DUE TO CREW REPORT OF BURNING RUBBER/ELECTRICAL SMELL IN THE CABIN AFT OF ROW 16. LAVATORY SMOKE DETECTORS DID NOT SOUND. MAINTENANCE FOUND VENTRAL AIRSTAIR ACTUATOR LEAKING AND APU INLET CONTAMINATED. PERFORMED OPERATION 5090 AND 5089 ALTERNATE AND FULL DUCT BURNOUT.