FWIW, my satnag is fine.
Have you ever tried it in Cornwall?
Mine only seems to use roads with grass growing up the middle.
I have, and it was fine. Better than me as it happens, as I chose to ignore it in Port Isaac, and ended up with less than a rizla between the rear wheel ache and a stone wall one side, and some scaffolding the other.
But mine is the older system, prone to butt frukkin' itself during map updates. Fortunately, I worked out how to manually copy the map onto the drive, though it means removing the hard drive from the IAM.
As from green grass up the road, I drive for miles looking for those sorts of roads