Vacancies, etc., not to invalidate proceedings of Board

No act, rule, or proceeding taken under this Act by the Board shall be invalid merely on the ground—

1. (a) of any vacancy or defect in the constitution of the Board, or
2. (b) of any defect or irregularity in election or appointment of a person, acting as a member thereof, or
3. (c) of any defect or irregularity in such act or proceeding, not affecting the merits of the case.