As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED LAVATORY SMOKE ALARM SOUNDED ABOUT 7 MINUTES INTO FLIGHT. NO SMELL OR SMOKE SEEN. NO MESSAGES WERE DISPLAYED. AIRCRAFT RETURNED TO AIRPORT LANDING WITHOUT ISSUE. MAINTENANCE TROUBLESHOT AND REMOVED AND REPLACED THE LAVATORY SMOKE DETECTOR. OPERATIONAL CHECKS WERE PERFORMED USING THE AIRCRAFT MAINTENANCE MANUAL. AIRCRAFT WAS RELEASED FOR SERVICE.