Alright, I have searched and found nothing on this specific item. When I am stopped at a red light, or stop sign, or a parking lot, the speed indicator shows anywhere from 0 to 8 mph and sometimes causes the route to recalculate. my VSS is hooked up to the harness. I have a 2008 VW Rabbit.

Seems like an incorrect pulse from the tacho.

When the tacho says to your navi the car is moving and you are standing still. after a couple of times it 'appears' you are off route / wrong road and starts recalculating.

Verify at your dealer if this really is the correct lead.

but is this probably also the reason why the map in 2D-mode sometimes "jumps back" a tad? I assume the position is extrapolated to a certain degree (which can be useful in short tunnels etc) and when the GPS signal is updated it realizes that the position is not correct and adjusts accordingly. Does that make sense?

Take the VSS wire out and see what if that fixes the problem.

If you are referring to me - I don't have the VSS hooked up (yet); was going to do it tonight though...

but is this probably also the reason why the map in 2D-mode sometimes "jumps back" a tad? I assume the position is extrapolated to a certain degree (which can be useful in short tunnels etc) and when the GPS signal is updated it realizes that the position is not correct and adjusts accordingly. Does that make sense?

That's entirely a possibility. GPS updates location only once per second, so software extrapolates position in between from щнгк estimated speed. When a new update comes, combined with inherent GPS positioning errors, it might make the map slide back a bit...