Vacancies, etc., not to invalidate proceeding of Appellate Tribunal

No act or proceeding of the Appellate Tribunal shall be invalid merely by reason of— (a) any vacancy in, or any defect in the constitution of, the Appellate Tribunal; or (b) any defect in the appointment of a person acting as a Member of the Appellate Tribunal; or (c) any irregularity in the procedure of the Appellate Tribunal not affecting the merits of the case.