Straight lines

[routeconverter]

That cannot be the whole story regarding zooming. I keep having the same straight line problem when I simply zoom once from a fully routed plan (i.e route between all waypoints has been calculated) but which results in straight lines replacing all or part of the route. If as you say there is no Google query when just zooming, surely the full route would never be lost just from zooming.

RouteConverter is Open Source. Checkout the code, analyze the problem and provide a patch or pull request if you have a fix.