As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT, AUTOMATIC PRESSURE CONTROL FAILED IN FLIGHT, CAUSING AN OVER-PRESSURIZATION OF CABIN. FLT CREW RETURNED TO DEPARTURE. TROUBLESHOT SYSTEM TO A FAILED CABIN PRESSURIZATION CONTROLLER. INSTALLED A REPAIRED UNIT. PERFORMED IN ACCORDANCE WITH GIV AMM 21-02-02.