I found this thread since I am about to replace my iPhone 6 - (one of the reasons is that the GPS is not working) and I wanted to know whether either the 8 or the X have the same problem.
I can confirm that for my iPhone 6, none of the iOS updates the last 8 months have fixed my GPS issue.
I rarely use any GPS functionality since I commute same route every day, and don't use apps like Pokemon Go, MapMyTracks or other training apps - so I really cannot tell how long my problems have existed, but for sure they were not present when the phone was new 3 years ago.
However, I really need the GPS from time to time, navigating in cities or finding addresses, and it is so frustrating not being able to trust on this feature.
My GPS problems is behaving just like described by many others in this thread. It is not limited to use in car - but also when walking, etc.
I can have occasional "blips" of GPS satellite signals. Last week when testing, I had two "blips" of GPS signals while driving a distance of 50 km (constantly moving the phone around in the car searching for signal)
My issue is definitively that the phone doesen't receive any satellite signal regularly. I use the "GPS Diagnostic" app, which show how many satellites it receives signal from (if any), and the signal strength. The above mentioned "signal blips" coincides with when the app reports satellite signal reception.
Needless to say, I have tried every tips and trick to re-initiate the GPS functionality (except hardware "operations"), but to no avail.
SO - now I wonder if it is worth the money to go for a 8 or X - or if I should downgrade to SE...