Hi, I've just purchased a 2012 slk r172 cdi . I have two issues with the audio 20 ntg 4.5 system, I hope someone can help me with.1. there is a becker map box and cradle fitted but when I select the Nav button, it displays no navigation. I have connected the box to my pc and it recognized the maps, I've also changed the battery in the box still no luck. 2. the DAB radio option is missing. It is present in the engineering mode and shows the dab channels it can find. It is just not an option for me to select only FM, MW,LW or SW. I have removed the system to check and all the connections in the back are in place.