Hi
I did an install of an MFD2 myself recently so;
1. Where did you put your antenna?
2. Check on the unit in the compass screen what it says regarding reception.
It will say NO_SAT, 2D or 3D.
When I did my install I put the antenna in the dash which gave poor reception, what the MFD2 does when it looses reception of the SAT signal is it uses "dead-reckoning" to determine your location from your speed and steering.
What I think is happening is that it is getting variable sat position and then loosing it so it is guessing where you are.
If you have had the antenna in the dash try putting it up in the headliner at the windscreen, it works great for me.
Regards
Dave N