As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MSN FLT 6120 - THE CREW REPORTED THAT DURING DESCENT THE CABIN WAS NOT DEPRESSURIZING. CABIN RATE VARIED FROM -1000 FT/MIN TO +450-500 FT/MIN. TRIED USING MANUAL CONTROLLER, BUT COULDN'T GET A NEGATIVE RATE. CREW ENDED UP DUMPING CABIN PRESSURE DURING DESCENT. MAINTENANCE REPLACED THE PNEUMATIC OUT FLOW VALVE. ALL OPERATIONAL CHECKS WERE GOOD.