As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - ON TAKE-OFF, CREW RECEIVED A MASTER WARNING FOR THE AFT SERVICE DOOR. MAINTENANCE INSPECTED AND FOUND FAULT FOR THE AFT SERVICE DOOR GAP TOO FAR. MAINTENANCE CLEANED THE PROXIMITY SENSOR AND TARGET. AIRCRAFT WAS PRESSURIZED AND AN OPERATIONAL CHECK WAS PERFORMED. NO FAULT WERE NOTED AND THE PSEU SHOWS THE GAP AS SATISFACTORY. AIRCRAFT RETURNED TO SERVICE.