While on a trip I set my retuen journey in advance, Centre of Thurso to Hesket Newmarket, avoiding motorways. I was staying in a hotel just outside of Thurso. On the morning of my return trip I selected the route, then rode to the centre of Thurso and started to follow the route. The route was simple for the first 200 miles, just follow the A9. Immediately I exited Thurso, on the A9, the 450 indicated that I should reverse direction at the next turn, and at every subsequent lunction and layby. Despite the highlighted route being the A9, when I got to the junction with the A99 it told me to turn left for Wick, rather than follow the A9 for Inverness. This continued for the next 200 miles to Perth, reverse direction at every possible junction an layby, destination distance increasing, time to destination increasing. At Perth I checkecd the route to see if I had accidentally set Thurso as my destination instead of Hesket - I hadn't. I hadn't set any waypoints either. What kind of nav software would do this? Surely after 200 miles into the journey it would recognise I was on the right route and correct accordingly, even if I had missed a phantom waypoint? What on earth was going on?