In appeals where the board finds that there is relevant evidence which, in the exercise of reasonable diligence, could not have been produced or which was improperly excluded at the hearing before the department, it may enter an order remanding the matter to the department for reconsideration in the light of such evidence. In all other appeals the board shall enter an order either affirming or reversing the decision of the department. When the order reverses the decision of the department, the board may direct the reconsideration of the matter in the light of its order and may direct the department to take such further action as is specially enjoined upon it by law, but the order shall not limit or control in any way the discretion vested by law in the department.