Google Maps in 4G Zones

When I travel to work on the Train in the morning, from the Suburbs to the City, my Mobile will go from a 3G network to a 4G network as I approach the City.

Starting in the Suburbs, Google Maps tracks my train journey nicely - 3G area.
However, once I see my mobile has entered the 4G (LTE) coverage area, I loose my position.
When I manually make Google Maps find me, It cannot.
I do not know if it's an App, Mobile (Sony V) or Carrier issue.
Any ideas ?

Update
I read that there may be issues with GPS and 4G. Found nothing conclusive yet.
In the City today (4G area), I see that Google Maps gives me "waiting for location......your current location is temporarily unavailable"
When I switch the Mobile to "WCDMA only" (3G), Google Maps picks up my location in seconds

I have seen Google Maps work in the City (4G) as recent as yesterday so i don't know why it is so unstable