Baffled by Navman routeing...

[Daytona]

I've got an iCN510 and am generally happy with it but still finding the choice of routes to be a bit strange and inconsistent at times.
Twice in whilst over in France the last couple of weeks in particular it showed inconsistant choices...
Driving from Beregerac to Duras we went on the main roads via St Foy except we were routed off just short of St Foy on roads which slowly reduced in width to little more than one car wide. Admittedly this "cut the corner" but were slower roads to drive on.
Heading from Duras to Monpazier, the distance to destination was more than I thought at 53 or so miles. Soon realised rather than a direct route over a good A road, it was taking me north, then east then south on similar A roads via St Foy and Bergerac again. Ignoring the "perform a U turn" instructions, it eventually recalculated and knocked over 20 miles off the journey....
And for 2 days it suddenly tried to route me up a very narrow sidestreet on our route back through Beregerac to where we were staying rather than stay on the main road as previously.
I do usually do a quick check on the route but sometimes the processor just seems to take an age to redraw the screen when following it.
Oh, and it would suddenly drop the GPS signal for no obvious reason and would need a hard reset before it would regain it.
Yet it routed us round Paris perfectly....

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