As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT THE CREW REPORTED THE EXTERNAL SERVICE PANEL ACCESS DOOR WAS OPEN. THE FLIGHT RETURNED TO ABE AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE DOOR AND FOUND NO DEFECTS. THE DOOR WAS PROPERLY SECURED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.