Roland VA-7 screen calibration

Hi, I have a VA-7 with a screen issue:- some icons do not respond to touch or respond by pressing the icon below them. Changing screens, changes the location of icons that do not work. The screen calibration also fails with “no calibrate”. I was told that this could be the 16Mhz or 20Mhz crystals rather than the capacitive screen sensor however they looked good with an oscilloscope. I’m not sure about replacing the sensor as I think the problem may lie elsewhere. Any ideas would be welcome.