In the event of an appeal by a contractor or the Government from a decision of any agency board pursuant to section
607 of this title, notwithstanding any contract provision, regulation, or rules of law to the contrary, the decision of the agency board on any question of law shall not be final or conclusive, but the decision on any question of fact shall be final and conclusive and shall not be set aside unless the decision is fraudulent, or arbitrary, or capricious, or so grossly erroneous as to necessarily imply bad faith, or if such decision is not supported by substantial evidence.