As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAS - AIR TURN BACK - FLT 0374 - CREW REPORTED THAT AT FL 300 CABIN ALTITUDE KEPT CLIMBING TO 10000', STARTED DESCENT AND CABIN WAS CLIMBING AT 700' PER MIN. MAINTENANCE PRESSURIZED AIRCRAFT IAW TASK CARD F1B21308 WITH AIRFLOW IN HIGH FLOW. OPERATIONAL CHECKS WERE GOOD.