Possible bad touch screen??

My TomTom One (3rd ed.) will not respond correctly to my inputs on the touch screen. If I press anywhere on the right side of the screen, it will only log a hit on the far left of the screen. I cannot access anything in the middle or right of the keyboard if I am trying to type an address. Some screens will not register a hit at all, which means I cannot proceed past them (toll screen). Everything else on the unit functions as it should. Is this a touch screen issue only, or possibly a motherboard issue? The touchscreen looks like it should be an easy fix, as long as I can figure out how to separate it from the LCD screen.