I have yet to be convinced that any sat nav is totally reliable, even for routes solo.
My wife always checks the route suggested by the satnav, against the good old map book, that is when towing, and sometimes solo.
With the old xtrail we had one occasion when the sat nav sent us in a circle!, we were solo so no problem, the satnav map even showed we had done a circle, we found it funny at the time.
The 2nd occasion was not so funny, we ended up going down a tarmac road that reduced to a single road, then a dirt track, which then turned into a nightmare track with deep holes everywhere, i crawled over that road expecting the xtrail to bottom at anytime, my back was covered in sweat, the reason we kept going forwards was it was easier than going backwards, and the map showed it was shorter to go forwards!
Unfortunately the road never did connect to the "main" road, it was blocked of by a great pile of rubble and soil!
So i had to do a ten point turn. And go back the way we had come.