OMG, TomTom, Why Did You Kill Your Product?
If I deviate from the route TomTom is recommending, something happens:
a) TomTom recalculates the route
b) TomTom stops giving guidance
c) TomTom tells that no route is available (even if driving on a main road)
d) TomTop enters an endless loop telling "finding the best route" and showing nothing useful on the status area. Must interrupt the guidance and recalculate.
I was driving last week 500+ kilometers from Hämeenlinna to Oulu. Within the first 200 kilometers, the action b) was taken once, the action c) once, and the action d) four times. Pretty annoying, and definitely not attributes of a high-quality product.
The reasons for the deviation were simple: Having a lunch in a restaurant close to the route, and mad routing.
Mad routing? Yes. TomTom should have a serious discussion with its map provider(s) in Finland: TomTom shows the 11 km section of 4/E75 as closed one because of roadworks (true), and the parallell deviation road as closed, too (not true). Thus, TomTom thinks that the principal national North-South corridor does not exist. Therefore, most of the long-haul N-S routings currently are pure bullshit. I got tired, switched to Google Maps, and remaining 300+ kilometers were ok.
TomTom routing Helsinki-Oulu, on primary, secondary and regional roads:

Google routing Helsinki-Oulu, on primary road 4/75 except at the roadworks:

Comments
Thank you for the detailed feedback! I"ve passed this to my team for further investigation.
Regards, lampard