As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING THE CLIMB THE AIRCRAFT EMERGENCY PRESSURIZATION VALVE OPENED WITH OUT BEING SELECTED. THE CREW DEPRESSURIZED THE AIRCRAFT AND RETURNED TO BASE. THE EMERGENCY PRESSURIZATION VALVE WAS REPLACED AND THE AIRCRAFT SYSTEMS FUNCTION CHECKED SERVICABLE