After purchase at one time seat heating defective and money back? !

Have a question, and recently I sold my car, probably already 2-3 months ago.A month after the purchase the buyer would write me an e-mail that both seat heaters are defective. With me she went in winter still impeccable but otherwise I do not use it. We have also contractually held motor and electronics in order and bought as seen. However, she was also not checked on her function when buying. Now after 2 months scrape Is he just having an appointment with the dealer and I should probably take over the damage? I already told him at the first mail that I didn’t know about these defective ones (if they even exist) Now my question, should I go directly to the lawyer? Or just ignore him? What do I have to fear? Mfg!