In over 20 years of consulting and thousands of assignments, I have only been sued once and did not loose. You'll notice that I did not say that I won because I was still out my court fees and a considerable amount of time that was diverted from my work. Only the attorneys won - at least monetarily. When confronted with what your client perceives as an error, act swiftly to assuage the situation. When someone perceives that you have made a mistake and it's costing them money, they are obviously going to be angry.
Situations have a way of becoming more inflammatory the longer they remain unresolved.
Like an infection they fester and get worse. Many appraisers and home inspectors who have ended up in court could have avoided it by promptly returning the phone call to their dissatisfied client. Follow up with a visit to the home the next day if possible. Throughout your discussions be professional and pleasant. Don't commit to any course of action until you have had an opportunity to view the conditions you purportedly missed.