The odd thing is to get to this point they would have had to pass the first set of exams which is generally harder.
They also have continual assessment throughout their time as a registrar.
If you flunk at the end its usually because of personal reasons. I suspect that there were issues with one or two of the questions.
The other thing is that the exams are written in a central location and all the candidates from round the country come to one of the universities to write. This then rotates every year with examiners coming from that university.
So one year it will be a UCT exam and the next a WITS exam, then UFS etc.... so would be interesting to see which university was hosting the exam this year.