As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE CLIMBING THROUGH 7500 FEET, THE FLIGHT CREW HEARD A LOUD POP THAT WAS FOLLOWED BY A HISSING SOUND COMING FROM THE CABIN DOOR. THE CREW RETURNED TO THE DEPARTURE FIELD AND LANDED WITHOUT INCIDENT. ONCE ON THE GROUND, THE FLIGHT CREW NOTED A SMALL GAP BETWEEN THE CABIN DOOR AND DOOR FRAME WITH THE DOOR CLOSED. MAINTENANCE TECHNICIANS REPLACED THE DOOR SEAL AND PERFORMED PRESSURIZATION CHECKS. THE DOOR SEAL FUNCTIONED PROPERLY AND THE AIRCRAFT WAS RETURNED TO SERVICE.