I have found that three or less satellite 'connections' cause the symptoms you describe, Snowball. The only time mine has been a waste of space was when I foolishly used it to try to drive to a Reunion in London. Being surrounded by tall buildings really messed it up. Because of parking restrictions in the area I was going to, i got a friend to drive my car home on the understanding he would collect me afterward. By some quirk of fate, he actually knew where I was heading, and took over navigation.
Rolebama, I was having difficulties in rural areas in France. Frequently, the unit asked me if I wished to start from my last known destination, and a 'yes' started to plan a route from my home address in England.
The TomTom technical contact was satisfied from my described circumstances that the equipment was faulty.
A pity, really, because my previous TomTom was exceptional in my opinion - even taking us down a gravelled path and into the parking area of a French campsite, in pitch darkness and just by entering the campsite GPS.
Main reason for the new unit is a lifetime free map updates, and at a discounted price that wasn't much more than buying updated maps for my old unit.