As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - FLIGHT 2271 - THE FLIGHT RETURNED TO GATE WHEN AFTER STARTING THE NR 2 ENGINE AND BLEED AIR, THE CABIN DESCENDED AT 3000 FEET PER MINUTE. MAINTENANCE INSPECTED THE AIRCRAFT AND REPLACED THE NORMAL OUTFLOW VALVE. THE OPERATIONAL CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.