I have loads of routes created in My Route App that I have used in Navigation prior to this update.
I have noticed that many of these will now not load with this update.
I am able to fix them by opening them on my iPhone 6 Plus in My Route App, changing the Map to Google then back to Here.
The route will then open in Navigation.
I have sent diagnostics for 3 routes that are affected on 23/02/2019 at around 11:30pm UK time.