My 2003 A6 1.9Tdi Multitronic has this faeture enabled however it seems a bit unreliable. It works for weeks, then stops working for weeks, then suddenly works for weeks again.

Where is the decision made? In the 'Convenience Module'?
Where does it get the 10Mph from? I assume an ABS sensor, but in which weel?

Does using the inside lock/unlock switch interfere with the set-up?

The speedometer is working correctly and there are no ABS warning lights.

Lucas