The inaccurate VSI situation has several possible outcomes:
Pilot decides he cannot safly fly the aircraft in that condition, and writes it up for repair before further flight = Outcome; did not go flying that day.
Pilot flies the aircraft as is, and so do the next pilots = Outcome; it never gets fixed.
Pilot goes flying that day, then tapes across the instrument "U/S", and snags it upon landing = Outcome; the next pilot decides he can still fly his next flight safely, and it probably gets fixed, or at least a error card, at the end of the day's flying.
Pilot (who is not a mechainic) decides to perform "do it yourself" maintenance under the panel = Outcome, he gets caught, and gets a bill for a complete inspection of everything under there which he could have affected, and the authorities discuss enforcement action for unauthorized maintenance, or; his faulty work goes initally un-noticed, then at the time of the accident investigation later, the unauthorized maintentance is discoverd to be a contributing factor. Very not good.
As a pilot, you have some latitude to decide to fly with a known defect, which will not affect the safety of the flight. You my just have to defend it later if challenged. If you have any latitude to go fixing the plane, you are formally qualified for maintenance, and you know exactly what privilages you have.
If you want the standards of servicability for an aircraft in black and white, you'll need to fly an aircraft with a published minimum equipment list, then there's no doubt.