well lets just put it into carputer plain english for you.
vibration plays a key role in touchscreens especially resistive ones simply because when you touch them they change the resistance (which current changes aswell) and causes fluctuations in power distribution. When you mount a touchscreen that is resistive and you get lots of vibration then it is randomly making contact causing a spike in current. They are less reliable because of this however cheaper to manufacture.
hope that explains it.