In the event a contract provides for the payment of any installment which is more than double the amount of the average of the preceding installments the buyer upon default of this installment, shall be given an absolute right to obtain a new payment schedule. Unless agreed to by the buyer, the periodic payments under the new schedule shall not be substantially greater than the average of the preceding installments. This section shall not apply if the payment schedule is adjusted to the seasonal or irregular income of the buyer or to accommodate the nature of the buyer's employment.