Without seeing it in person I can only give an opinion coming from 33 years in the OEM paint industry. Usually adhesion failure on plastics is due to the plastisizer coming out of the plastic which causes the clear coat to loose its bite to the substrate. That is why you dashes gets hard and crack, steering wheels get sticky. Unless you can pick away the remaining clear coat mechanically, your only other option would be sand it off which will effect the plastic. Clear coats for interiors on plastics are usually a UV cured clear.