If you only fail once in a while, that's not a problem. Some of the audits are really hard to identify as such (or correctly pass, for that matter), because they're based off individual decisions, not necessarily agreed-upon policy.
If you fail too many – and nobody really knows that number – you will be banned from reviewing only. No other restrictions will be in place, so it's not comparable to a full account suspension.
The algorithm is as follows: Given a 30 day window, the first ban will get you 2 days. The second one 7 days, and the third one 30 days.