Why does my ceramic coating bead well on some panels but not others?

Different panels age at different rates. Horizontal surfaces such as the hood, roof and trunk receive more UV exposure, heat, bird droppings and mineral deposits, while lower panels collect more road film and tar. Panels that were polished, repaired or repainted after coating may no longer be coated at all. Decontaminate the weak panels and compare again; if they still underperform while protected panels behave well, localized wear or removal is the likely cause and that area can be recoated.