Don't fret, you're not alone, all of us have failed the occasional tricky audit. Some of thenthem are, what I call bad audits, but to stop people from robot reviewing they are a good thing and that is what counts. Being myself annoyed with audits from time to time, yep even failing some. Doesn't keep me from reviewing.
One rule of thumb you should go for when reviewing, when in doubt, re read-read the question or answer in its original form, this is what the Link link is for beside it.
Check its edit history if your still in doubt then, maybe a flag or vote was cast on an question/answer in a much worse state and an edit resolved that later on.
And all be the way you will catch the audits in most cases and not fail them. so you payed attention to an question/answer. As we should put research into our questions we ask and answers we give, reviewing others needs as well the same kind of research.