As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT 13,600 MSL CREW RECEIVED A CABIN PRESSURE WARNING MESSAGE. CREW DROPPED TO 10,000, REGAINED CONTROL OF PRESSURIZATION AND CONTINUED TO DESTINATION. WHILE CLIMBING AGAIN, PRESSURE DROPPED AND CREW ELECTED TO RETURN TO DEPARTURE WHERE THEY LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED, R & R AFT CARGO DOOR SEAL IAW AMM AND OPS CHECKED GOOD.