If a vacancy occurs on such court at any time prior to the final disposition of the case and the completion of all duties required to be performed by it, the court shall not be dissolved and the proceeding shall not fail; the vacancy shall be filled by designation of another judge from the panel provided for in this chapter. Such substitute judge shall have all the power and authority of his predecessor, and the court shall proceed as so constituted to hear and determine the case and do all things necessary to accomplish its final disposition and the completion of all the duties of the court, including such matters as the certification of evidence and exceptions. No decision shall be rendered or action taken after such designation with respect to any question previously submitted to but not decided by the court except after a full hearing in open court by the court as reconstituted of all the evidence theretofore introduced before the court and a hearing of all arguments theretofore made with reference to such question.