TT XXL displays an incorrect car speed
What is more strange, it seems that the XXL "knows" the correct speed, but is slow in displaying its variations. In fact, if the speed limit in that point is (say) 130 km/h, and I go over 135 km/h (as shown by the car speedometer, also considering the speedometer systematic error), the red alarm light immediately switches on; but, at the same moment, the speed shown by XXL is, for instance, 120 km/h!! then, slowly (some minutes), the displayed speed raises to a credible value.
Anybody can help me?