“When a party objects to a magistrate’s judgment on the ground that the judgment contains insufficient factfinding, the party should file an objection pursuant to Rule 118(a) and specifically assert that there are insufficient findings to support the magistrate’s judgment. The reviewing court can then adopt the judgment, ‘set the matter for further hearing before a judge or magistrate[,] or recommit the matter to the magistrate with instructions.’ M.R. Civ. P. 118(a)(2),” Associate Justice Catherine R. Connors wrote on behalf of the unanimous court.