As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURN TO FIELD DUE TO A PRESSURIZATION PROBLEM. CFDS REPORTED NO FAULTY SYSTEMS OR COMPONENTS. GROUND TESTING OF CABIN PRESSURE CONTROL, FMGC, AND ADIRS SYSTEMS REVEALED NO SYSTEM FAULTS. REPLACED CPC 2 AS PRECAUTIONARY MEASURE AS THIS WAS CPC IN CONTROL AT TIME OF EVENT.