There are far less JCV images available for your 42 compared to your 3790. Re your pics in Post #159, when scrolling thru a [simulated] route on your 42, you need to press the 'junction view' words at the base of the screen when they turn bright to see the jcv image. It's different to your 3790 display in that respect where the image is displayed without that prompt.
Hard reset your unit after you back everything up if reinstalling GE didn't help, and then try again for the map update. You can restore your favourites later if you want.