Disclosure, disclosure, disclosure! If these were existing issues prior to selling the home and you disclosed them... then the buyer should already know about them and you are covered. If they are new issues which never previously occurred and have happened since the purchase of the home then you could not have disclosed them. However, if these have been ongoing issues that you did not disclose during the sale, the buyer has a case.
The buyer's only recourse is a suit at this point. The buyer will need to prove that you were aware of these issues and did not tell them. If an inspector goes and and finds evidence that this has been a recurring issue the buyer can prove his case.
I would get all my documentation together and have an attorney in mind if it comes to that. Good luck!
Better Homes and Gardens Real Estate Town & Country