I'm not doing a true nearest neighbour algorithm to find where we are in the route. Right now it basically walks the route from the currently chosen 'closest' point until it finds one that is closer. As a result, the first location update after selecting a waypoint closer to the start will basically bring you back to where it was previously.

Selecting upcoming waypoints is easy because I don't search backwards for a better point. This right now is more art than science, I've tweaked that code in pretty much every release.

The version you reloaded probably has a problem that it doesn't automatically switch to the next point while you are driving if you pass the point at some distance. Another version was picking points way up ahead if there was a curve in the route, etc. Maybe I should do something like disabling the automatic search when the knob is turned and reenable it on a knob press.