I think I have the reason why this occurred as well as the solution. I was unaware of the possibility to download maps and run navigation in the off-line modus, using the downloaded maps. So whenever the on-line connection of my iPhone stopped, I guess the map on my CarPlay display went black. I have now downloaded offline maps for the countries I drive in and selected the option ‘navigate in offline mode’ and this black screen issue has not reoccurred. Case closed as far as I am concerned.
