I had better luck with a better route planner ABRP (abetterrouteplanner.com). On my last long trip the built-in planner had me take some strange route and 15 hour travel time. ABRP was 12 hours and worked great. If you want to run the app in CarPlay, you have to pay, but it's free on your phone.
I’ve had an easier time planning longer drives since I started using smartevroute.com because it lets me play with things like starting charge, reserve, and max charge at stops without feeling lost in menus. If your route keeps giving odd results, I’d try resetting the inputs, then slowly adjusting range and reserve until the map updates the way you expect.