That's like blaming Microsoft because you're having problems with Firefox. Sync is an application running on Windows CE, developed by a company other than Microsoft. While QNX is a solid OS, it's not a given the next gen Sync while be any less buggy.

Have you tried updating the software since purchasing your truck? The Sync version that shipped with your vehicle was loaded with errors, but a significant suite of updates squashed a lot of bugs, possibly even the one you're experiencing.

Yes, both are always used, but what I described above was a corner case where GPS is unreliable, with a good signal too, for a long stretch so DR has to be solely relied upon, unlike what you suggested earlier that positioning be biased toward GPS. In that example, GPS had preference and was positioning the vehicle in the river. Because situations like this occur regularly in large cities, in addition to a lost GPS signal, positioning is more accurate when biased toward DR.

Without good DR you don't have to lose a GPS signal in a large city for a nav system's positioning to utterly fail. An Urban Canyoning effect can render GPS unreliable despite a strong signal. I've seen GPS in a mile long urban canyon position a vehicle in and across a parallel river in the middle of the canyon. The ultimate solution when this behavior is detected is to rely solely on DR, which in practice can go days of driving before being significantly inaccurate.

The automotive nav system I work on has 2D dead reckoning, relying on GPS for altitude. 3D dead reckoning is news to me, and I suspect is the intended newsworthy bit here. When GPS fails and the digital terrain model doesn't account for urban landscapes like parking garages, both above and below ground, and tunnels, positioning is calculated in software. It's an expensive, imperfect process I imagine can at least be offloaded to sensors, if not improved, as possibly done in this chip. That would certainly free up the radio to provide more accurate positioning and guidance quicker.