If by reason of death, sickness, or other disability, a judge before whom an action has been tried is unable to perform the duties to be performed by the court under these rules after a verdict is returned or finding of fact and conclusions of law are filed, then any successor or special judge sitting in or assigned to the court in which the action was tried may perform those duties; but if such other judge is satisfied that he cannot perform those duties because he did not preside at the trial or for any other reason, he may in his discretion grant a new trial.