As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5307 - CABIN PSI ROSE RAPIDLY, AT 10000 FT CABIN PRESSURE ALTITUDE WAS 8800. NO MESSAGES RECEIVED. RETURNED TO ATL, LANDED WITHOUT INCIDENT. PERFORMED BITE CHECK OF ACSC, PASSED. REPLACED ISOLATION VALVE. GROUND PRESSURIZED A/C. NO FURTHER DEFECTS.