WIN CE NextGen on S100 stereo: cant go back to GPS

Hi! i have been using NextGen on my S100 for a few months and really like it.
I tried two versions with similar results, here is the problem:
The app runs and works very well, but if I leave the GPS app, for example pressing the stereo's button to go to the home screen or to the audio player, I can no longer go back to Nextgen! when I try to go back (pressing the stereo's Nav button) it just goes to the home screen.
Weirder yet, the app seems to keep running fine in the background, as i get audio notifications for cameras or if I lose the signal when entering my garage.
Any ideas? it's very frustrating as even if it works great, if I have to do whatever with the stereo (even putting the car in reverse, which switches to the backup camera), the only way to go back to Nextgen is to reset the unit.
This does NOT happen when using Primo, I can go back and forth between the GPS and other stereo's options.

Another, minor issue: I'm stuck using Here 2014 q2 as I can't find a newer license for Argentina maps, is anyone aware of a license for 2015/6 maps (Here or TomTom)?

thanks in advance!