As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 783 - DURING CLIMB-OUT FROM BOS, CREW NOTICED A LEAKING AFT SERVICE DOOR SEAL. NO DOOR INDICATION WAS PRESENT IN COCKPIT. ONCE CREW WAS UNABLE TO PRESSURIZE AIRCRAFT, CAPTAIN ELECTED TO RETURN TO FIELD AT BOS. FLIGHT LANDED WITHOUT INCIDENT WITH NO EMERGENCY BEING DECLARED. MAINTENANCE REMOVED DEBRIS FROM AFT SERVICE DOOR JAM, LEFT SIDE. LEAK CHECK GOOD. (M)