A magistrate has to be considered like a judge, with ability and power to make findings of fact. In plain English, the magistrate determines what the facts are (what happened) and then applies the facts to the law and makes a recommendation to the judge.
As the fact-finder a magistrate can reject testimony that he or she disbelieves. The finder of fact is not required to believe the testimony of any witness. Even if the testimony is “uncontroverted”; the magistrate can simply believe it, or not. That is the authority given to the fact finder.
In a recent case: the husband had a substantial decline in income from his business (operated as a sole proprietor); the witness (husband) was simply not believable and his testimony was not believed by the magistrate.