As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GEG - FLIGHT 2353 - THE FLIGHT RETURNED TO FIELD AFTER THE CREW HEARD A LOUD POP AND THE AIRCRAFT RAPIDLY DEPRESSURIZED. MAINTENANCE INSPECTED THE AIRCRAFT AND REPLACED THE AFT CARGO DOOR SEAL. OPERATIONAL CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.