I occasionally get transient routing server failures, sometimes several in a row. It eventually works if I keep trying. However, it's frustrating to do this, especially if I've already started moving my car while waiting for routing to complete. It can also be really irritating if I stray from the marked route, prompting a re-route. If that fails, it then cancels navigation until I manually restart it, which means either fiddling with the stuff while driving, or finding a place to pull over.
It would be great if, when routing fails, the app would keep retrying until it succeeds, without my intervention. After all, I still want to go to the same place!