It shall be the duty of the trustee whose powers have been suspended as provided in this act, to deliver all property in his possession belonging to the trust administered by him to the co-trustees or substitute trustee, and to make and file an accounting within 30 days after the issuance of the order suspending his powers, or within such time as the court may direct: Provided, however, That his failure so to do shall not in any manner affect the validity of any power exercised or act performed by such co-trustees or substitute trustee in the course of the performance of the duties of their office. Such accounting may be lawfully made and filed in behalf of said trustee engaged in war service by his agent thereunto duly authorized in writing.