Google maps downloads maps for offline use but will not navigate when offline

I’ve downloaded local area map (entire city and surrounding region) for offline use, I can turn off all data / wifi and can pan around and zoom in and out of my downloaded area all fine.

Sometimes I hop in the car with no Internet and try to navigate it doesn’t work. It doesn’t recognise business names and it gives me a no internet error.

other times it works fine and navigates based on address or business name.

please don’t tell me how to download maps for offline use.