ESA MEDICAL ASSESSMENT

My son has adult ADHD, speech impediment and other mental health issues. He has violent outbursts especially in stressful situations and more so if he feels questioned or criticised. I had to finish a mental health assessment after he threw a chair across the room and stormed out. Long story short, he cannot attend a face to face assessment due to his mental health and condition. The Independent Health advisory is insisting he attends, despite requests ffom the ESA dept at the DWP and myself. There medical evidence is a sick note from 2015, information from out GP who has nothing whatsoever to do with his treatment it is all Consultant led and advice that his ADHD is improving. ADHD never improves you just find better coping mechanisms as time goes on. They have refused a home visit due to the risks . Anyway we are now being sanctioned. Can anyone give advice please. I have tried every avenue and have contacted our MP .