By using Google maps, the FP4 is just totally useless in my case.
I cannot drive nowhere, because by using a car or a bike im way to fast for my Phone.
The Location dot just stays somewhere on the map but will not follow the actual route.
Also it happens that it just doesnt go on the route at all.
Not good to hear, especially as my daughter gave up her FP3 because of a similar situation.
However it seems not everyone has this problem, so I imagine you will get help.
Can you specify if you use the standard FP system or any other ROM? Whats the Version you have installed (settings-about the device-build number)? Is this a new bug or from beginning (if you use the phone already some time)? Do you get a GPS Fix before you start your journey and how long does it take to get the fix? What are your settings for location, do you e.g. use Google Accuracy?
There are several settings (use Wifi and Bluetooth and Google location Accuracy) you can enable to improve GPS fixes under settings-location. If not done yet, maybe try to turn on.
Else I would try to use another Navigation App, to see if its Google Maps related or not. An App thats quite similar to Google Maps is Magic Earth.