The issue I am having is when i bring the map up, whether I have a destination put in or just viewing the map, the little black dot within the vehicle arrow doesn't stay stationary. when i start driving the dot moves forwards and backwards within the arrow and i think this is causing it to be inaccurate. A friend of mine has the same unit and the dot in his stays stationary. Is this something to do with the reverse sensor or do i need to add an additional accessory? Please help because this has been bothering me for a while.