Section 29. A. The violation of sections nine, ten, eleven, thirteen, fifteen, sixteen, seventeen, eighteen, twenty-six or twenty-seven by any person shall bar his recovery of any finance charge, delinquency or collection charge or refinancing charge on the retail installment sale agreement or on the revolving credit agreement, or on the sale pursuant to a revolving credit agreement, but such violation shall not bar his right to (a) recover from the buyer an amount equal to the unpaid principal balance or (b) repossess the goods and recover from the buyer an amount equal to the unpaid balance less the proceeds of any disposition of the goods.
B. Subsection A shall not apply to any violation which any holder shall establish by a preponderance of the evidence to be the result of accident or bona fide error in (a) any mathematical computation, (b) the layout or format, size of type or order of clauses contained in such retail installment sale or revolving credit agreement, or (c) the failure to furnish the buyer any statement required by section nineteen or by subsection D of section twenty-seven.
C. An agreement made by any person subject to this chapter which violates the provisions of this chapter may be declared void by the supreme judicial or superior court upon a civil action brought by the buyer.