As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE AT FL 370 LAVATORY SMOKE MASTER WARNING. A PERSON HAD JUST ENTERED THE LAVATORY FLIGHT ATTENDANT REPORTED. NO SMOKE OR SIGN OF SMOKE. STAYED ON FOR 15 SECONDS. REMOVED FROM SERVICE. PERFORMED FUNCTIONAL CHECK OF AFT LAVATORY SMOKE DETECTOR REF E175 AMM TASK 26-14-01-720-801-A. FUNCTION CHECK GOOD. A/C OK FOR CONTINUED SERVICE.