Depending on how rad-hardened the components are, I’m guessing it has a suffered a few DBEs. Some encoders/decoders in the transmit chain are hosed.
DBE Disadvantaged Business Enterprise
DBE Dame Commander of the Order of the British Empire
DBE Database Engine
DBE Deutsche Gesellschaft zum Bau und Betrieb von Endlagern (German society for building and maintenance of garbage final storage places)
DBE Direktoratet for brann- og eksplosjonsvern (Norwegian: Directorate for Fire and Explosion Prevention)
DBE Department of Border Enforcement (Iraqi border guards)
DBE Disabled Business Enterprise
DBE 1,2-Dibromoethane
DBE Daughters of the British Empire
DBE Design Basis Earthquake
DBE Department of Business and Employment (Australia)
DBE Design-Basis Event
DBE DFAS Business Evolution
DBE Double Bond Equivalent
DBE Degenerate Band-Edge (photonic crystal)
DBE Data Bus Element
DBE Double Below Elbow (amputation)
DBE Distorted-Wave Born Exchange
DBE Directorate of Border Enforcement
DBE Departmental Budget Estimate
DBE Dynamic Bias Estimator
I think you’re right. Time to send a repairman out to perform maintenance.