The problem is caused by a loss of adhesion or delamination of the inner & outer screen, when this happens you usually have a loss of response in the affected area with no physical signs of a defect. The app radio screen issue is really unusual due to the fact you can actually see the affected area.
The last resort repair method only works on resistive touch type screens.
The last resort repair attempt method is to remove the touch screen from the unit & separate it from the lcd screen, then place the glass screen on a perfectly clean flat surface, apply heat over the entire sc