Used camera sold on A7 iii olx on cod - the buyer says it's damaged

So I sold a camera on Olx , I have had sent him all the information to the best of my knowledge. didn't the fungal issue i knew about , I sent him all the footage he asked for and even more than that , I tried my level best to make it right for him from generating bills to arrange a cod purchase as well. Now when he got the camera there turns out to be more issues than i genuinely knew about. Now he is saying he will move legally or wants me to pay the repair cost , what should I do ?