KENV : Nothing that occasional re-calibration wouldn't fix.
Occasional? Keeping the system up and accurate requires more than occasional maintenance.
Then look at it from a manager's point of view. What does this system do, REALLY? It backs up the pilot/FE to a make sure they made no gross errors. That's a lot of expense to check up on pilots that cost the airline a lot of money. Putting in a good procedural cross check (rather than a hardware cross check) is likely more effective AND cheaper.