I have posted this problem before but it doesn't seem to appear on the page.
The navigation app doesn't appear to function with the screen locked, I will get maybe one voice prompt but the nothing.
The advice was to uninstall and reinstall the app, I have done this and the problem persists.
Koen Meijering (MRA)
about 1 month ago
I have made a ticket of your question. This will make it easier to help you.