Provided that no order of dismissal has been entered, when there has been default in the serving and filing of a brief within the time fixed by § 15-26A-75, counsel may stipulate in writing waiving such default; and if there shall be attached to such stipulation an affidavit setting forth facts constituting reasonable excuse for such default, the court or Chief Justice may, in its or his discretion, make an order excusing such default and extending the time for serving and filing such brief.
SDCL 15-26A-77