Section 623. Decisions final

1. A decision of a referee, if not appealed
  from, shall be final on all questions of fact and law. A decision of the
  appeal board shall be  final  on  all  questions  of  fact  and,  unless
  appealed from, shall be final on all questions of law.
    2. No finding of fact or law contained in a decision rendered pursuant
  to this article by a referee, the appeal board or a court shall preclude
  the  litigation  of any issue of fact or law in any subsequent action or
  proceeding; provided, however, that this subdivision shall not apply  to
  causes  of  action  which  (i)  arise  under  this article, (ii) seek to
  collect or challenge liability for unemployment insurance contributions,
  (iii) seek to recover overpayments of unemployment  insurance  benefits,
  or  (iv)  allege  that  a claimant or employer was denied constitutional
  rights  in  connection  with  the  administrative  processing,  hearing,
  determination  or  decision  of  a  claim  for benefits or assessment of
  liability for unemployment insurance contributions.