As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ISSUE- CREW REPORTED DURING CLIMB OUT PRESS AUTO FAILED ERRATIC CABIN ALTITUDES AND CABIN SIGNIFICANTLY HIGHER THAN SCHEDULED. CABIN ALSO CLIMBING AT VERY HIGH RATE, WITH MINIMAL AIRCRAFT CLIMB RATE. CREW RETURNED TO LAS VEGAS. CORR ACTION MX PERFORMED PRESSURIZATION CONTROL SYSTEM OPS TEST. FUNCTIONAL TEST IN AUTO MODE WITH NO DISCREPANCIES, FUNCTION TEST PASSED. AIRCRAFT RETURNED TO SERVICE.