Yes a bit of a strange one.. Its all academic now as I figured out how to make it boot to Primo but bricked the device in the process! I noticed there was another executable mgnshell.exe in the APP directory so as an experiment I renamed it to mgnshell123.exe and renamed the Primo executable to mgnshell.exe
On a restart the device booted up straight into Primo but now without mgnshell running there is no way to get back into the file system as it is no longer recognised by my PC, hence no way to turn on the camera and no way to update the maps.
At least now anybody else who come across this thread has been warned