I think a large part of this is simply that HERE's maps database isn't identical to Google's (or Apple's). There will be differences.
In the USA, most use Google Maps to look up locations and plan routes. The remainder use Apple Maps. Almost no one uses HERE maps. "Send to car" is bound to have issues unless the car is using the same maps database as your phone or desktop computer. It will mostly work if you are routing to a simple address, and rarely work if you are routing to a landmark name, trailhead, etc.
The best fix for this is for the automaker to use Google Maps database, as does Tesla (though with a proprietary routing engine), or has native Google Maps and navigation - as do Volvo, Polestar, and soon, several others.