Hi there Gardenstatejerseyboy,
Family Sharing shouldn't be related to the issue you're describing with navigation apps on your iPhone. We'd like to learn more to see how we can help. Does this happen in all locations or only when you're traveling in your car? What kind of signal strength are you seeing for your cellular network connection when this happens?
Also, make sure you have Location Services turned on for those apps in Settings. Learn how using the steps below:
How to turn Location Services on or off for specific apps
1. Go to Settings > Privacy & Security > Location Services.
2. Make sure that Location Services is on.
3. Scroll down to find the app.
4. Tap the app and select an option:
* Never: Prevents access to Location Services information.
* Ask Next Time Or When I Share: This allows you to choose Always While Using App, Allow Once, or Don't Allow.
* While Using the App: Allows access to Location Services only when the app or one of its features is visible on screen. If an app is set to While Using the App, you might see your status bar turn blue with a message that an app is actively using your location.
* Always: Allows access to your location even when the app is in the background.
You'll find that information in this support article: Turn Location Services and GPS on or off on your iPhone, iPad, or iPod touch - Apple Support
Next, make sure that cellular data is turned on for each of these apps with the guidance in this link: Use cellular data on your iPhone or iPad - Apple Support
Let us know how it goes.
Thanks!