As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT CRUISE ALTITUDE, CABIN PRESSURE BECAME UNCONTROLLABLE IN AUTO MODE. FOLLOWED COM PROCEDURE. AIRCRAFT DESCENDED TO A LOWER ALTITUDE AND CABIN PRESSURE WAS MAINTAINED WITH AUTO CONTROLLER. MADE AN UNEVENTFUL LANDING IN MKE. MAINTENANCE REPLACED NR 2 CABIN PRESSURE CONTROLLER. AIRCRAFT RETURNED TO SERVICE.