An employee rejected during the probationary period from a position to which he or she has been promoted shall be reinstated to the position from which he or she was promoted, (this shall include an employee rejected under Section D, because of not obtaining a certificate or license) unless the employee is discharged for cause as provided in this Agreement. In exceptional cases and by mutual agreement of the parties to this agreement, an employee who voluntarily demotes from a promotion may be returned to the promotion list.