As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO JFK DUE TO CABIN PRESSURIZATION PROBLEM. PER FLIGHT CREW: AIRPLANE UNABLE TO HOLD CABIN PRESSURIZATION WITH INDEPENDENTLY SELECTING EITHER LEFT PACK OR RIGHT PACK ON. CABIN PRESSURE NORMAL WITH BOTH PACKS SELECTED ON. CABIN ALT WARNING, UNABLE TO MAINTAIN PRESSURIZATION ON LEFT PACK. CREW SELECTED RT PACK ON TO MAINTAIN PRESSURIZATION. REPLACED WATER INJECTION LINE RT PACK