The navigation screen on my 2006 RX350 used to revert to the map after about 30 seconds on another screen (Audio, Climate etc). I changed it so that it would not revert, but now I can't remember how to change it back again. (Brain cells must be disappearing rapidly with old age ) I can't find any mention in either the car manual, nav system manual or even the Vais Soundlinq manual. Any ideas?