As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR INTERRUPTED BACK TO ORD WITH A CABIN PRESSURIZATION ISSUE. CABIN ALTITUDE HIGH ON DEPARTURE DECLARED EMERGENCY.-C/A-CONFIRMED MEL 21-22 MAINT PROCEDURE HAVE BEN REV. PERFORMED PRESSURATION CONTROL SYSTEM OPS CHECK IN MANUAL M/M TASK 21-31-00-700-801A AND PRESSURATION CONTROL SYSTEM FUNCTIONAL TEST IN AUTO MOD IAW TASK 21-31-00-700-802A OPS CHECK GOOD