As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING FLIGHT WHEN THE ACM WAS SELECTED TO THE FULL COLD POSITION, CABIN PRESSURIZATION WOULD BE LOST. DURING TROUBLESHOOTING, MX PERSONNEL FOUND A CRACK ON THE ACM INSULATOR. THE ACM WILL BE REPLACED PRIOR TO ACFT BEING RETURNED TO SERVICE.