Grounds of appeal.

No decision or award of the Board shall be modified or set aside in appeal, except on any of the following grounds:-

(a) such decision or award was improperly procured,

(b) corruption or misconduct of the Board or any member thereof, in the conduct of the proceedings relating to such decision or award,

(c) any illegality or irregularity in the proceedings relating to such decision or award, which has occasioned failure of justice,