JJFC
If you KNOW an instrument is faulty - are you seriously suggesting we follow it? I hope I'm misunderstanding you here, because any pilot is potentially 100% more reliable than a faulty instrument!
And unfortunately it's not always clear cut. Contradictory indications often occur.
Which instrument to believe then??
Then it is down to the skill and experience of the human at the controls, and he may have to utterly disregard the instrument right in front of him which is screaming for his attention. No easy feat, at the best of times.