> " it’s very unlikely that both would provide the same erroneous readings. "

You're assuming that faulty sensors will tend to have random output. But since we're talking about a real life mechanism, it seems likely it has some erroneous states that are more likely to occur than others. For instance if the mechanism often fails up against one of it's mechanical limits, the sensor might erroneously read out the limit position every time.

You can't actually say anything about the distribution of failure states for a sensor without evaluating that particular sensor.