[dghlsakjg]

They hadn’t had unexpected depressurization. They had an error in one of the redundant automatic controllers for pressurization. That controller isn’t even required equipment.

Airplanes fly around ALL THE TIME with equipment that isn’t working. They have a procedure for determining what is and isn’t necessary for a given flight both legally and by the airlines own standards. In this case it very much looks like the pressurization controller was a red herring.