Sub-Zero runs two entirely separate cooling systems, one for the refrigerator and one for the freezer. That is why food keeps so much better in them, and why a fault on one side leaves the other working perfectly — behaviour that confuses technicians expecting a single system.
These are built-in units worth many thousands of dollars, designed to be maintained for two decades rather than replaced. We service them accordingly: proper diagnosis of the affected system, genuine parts, and careful handling of the cabinetry they are fitted into.