It happens - sometimes. But not often. But if I remember correctly, a re-mark probably won't help you. You'll need to dispute a question. Even then, "wrong" questions have been known to stay in the question bank for months. My met exam was a case in point. Statistics are released on number of passes / failures and highest marks acheived. Each paper always has at least one person get 100%. My met paper had a number of people (including myself) get 99%. NOBODY got 100%. IMHO there was an "impossible" question. Impossible because the answer sheet has the wrong answer.