Any judge of a probate court who has commenced a hearing in any contested case shall have power to continue the hearing and shall render a decision not later than one hundred twenty days from the completion date of the hearing. If a judge of a probate court fails to render a decision within one hundred twenty days from the completion date of the hearing, any party may petition the Probate Court Administrator for relief which may include reassignment of the case to another judge. Failure of a judge to render a decision in a timely manner does not deprive the court of jurisdiction over the case. The parties may waive the provisions of this section.