Iphone 5S, GPS is not accurate

I have iphone 5s (ios 8.1.3), lately I started using a navigation app and noticed that my GPS signal is not accurate means that the speed is not working and my position is stuck or moves slow.

I downloaded some other GPS apps to make sure it isn't an app problem, same behavior. I used some GPS tools (such as GPS status app) and noticed that I'm getting only 65 meters accuracy while using another iphone (with the same app in the same location on the same time) I'm getting less than 10 meters accuracy.

I did try to hard restart, turning off and on the location services and some more tips I found in the web - nothing helped. I even tried to restore my iphone and test my GPS on a clean iphone to find the same problem.

Everything (Wifi, Bluetooth, 4G, 3G, etc.... ) are working just fine on my iphone.

Is it an hardware problem? how can I fixed it? ** my warranty already expired ...

Any help will be appreciated.