Problem with car loan

[nkg554]

My mother paid off her car loan in 7/2005, and the bank received her payment before the payoff amount changed. The bank debited the July payment from her account after the loan was paid off, but the bank would not pay it since they'd been notified that the loan was paid off. They sent a letter on July 12, 2005 along with a release of lien telling her that the loan was satisfied. Last month she received a letter from the bank telling her that she now owes the June 2005 payment and that the release of lien was null and void. She provided the bank with copies of her bank statements showing they debited her June and July 2005 payments, and they're still telling her she owes the payment. I called the bank for her and got the payoff in July 2005 and she sent a cashier's check at that time. Can they come back 2 years later and say the release of lien is not valid? As a side note, she sold the car in July 2005.