Is my customer legally entitled to a refund or other compensation on an AS-IS car purchase?

Is my customer legally entitled to a refund or other compensation on an AS-IS car purchase that occurred 5 months ago? I own a small dealership in NC, I had a customer who I have sold a total of 2 cars to in the past (sold in a buy here pay here type financing contract), the first car they purchased (which had a salvage title) was traded back in to us only a month later after purchase because the customer liked another car on our lot better than the one they currently had, so they traded the car back in and now 5 months later they are having transmission problems with the second car and came in to my office claiming that the first car was sold to them without disclosing that it had a salvage title ,(we have the signed documentation in file that clearly states the car has a salvage title and that they acknowledged that fact) now they claim that they have spoken to an consumer rights attorney and the NC General Attorney's office who advised them to get their money back from us for both purchases or otherwise they file suit against the dealership, both cars were sold AS-IS with no warranty so I don't believe that we owe anything to them but I'm not a contract professional and would like to hear professional opinions, thank you in advance for your time and effort to help me figure this out and God bless you.