If any compensation payable under the terms of a final decision or judgment is not paid by a self-insured employer or an insurance carrier within thirty-one days after it becomes due, as provided by the final decision or judgment, or if any temporary total disability benefits are not paid by the employer or carrier within ten days, exclusive of Saturdays, Sundays, and holidays, after the employer or carrier has been notified of the disability, and where the right to benefits are not controverted in the employer’s initial report of industrial injury or where temporary total disability benefits are terminated in violation of § 386-31, there shall be added to the unpaid compensation an amount equal to twenty per cent thereof payable at the same time as, but in addition to, the compensation, unless the nonpayment is excused by the director after a showing by the employer or insurance carrier that the payment of the compensation could not be made on the date prescribed therefor owing to the conditions over which the employer or carrier had no control.