Iphone 8 GPS not working

The GPS on Google Maps, Apple Maps, and Waze is drifting, and at times ou ty up to 25 kms.

So, after much troubleshooting and searching online, I tried absolutely everything possibly conceivable. Finally tried swapping out the device for a new one, and no success at all.

I then tried the device in a colleague's car and it miraculously worked, together with hers.

Following that experiment, I tried the device alongside hers in my vehicle, and hey presto, the GPS on neither devices worked.

Both of us have Android phones, and they worked well in both vehicles, both of us had iphone 6S's and both worked well in both cars, on iOS12.1.

Any ideas?