ahh so BEFORE W8.1 gps was always working FINE ? in your case can you confirm that is is related to OS update only...therefore being a SOFTWARE issue ?
also was it the first update or the latest denim update that started giving issues ?
do you have cases where you can't lock on at all, like most of us ?
have you tried W10 insider to test if things get better ?!
what does apps like "hardware tests" or "gpsinfo" indicate ???
When I bought the phone it had 8.0 and I used PfD to get 8.1 immediately. GPS worked fine, but I had lots of random reboots, and the touch screen would lock up all the time, so I was constantly rebooting anyway.
When 8.1 was officially released for my phone, there was also a firmware update to fix the touch screen issue - but you could only get it with the official 8.1, not PfD. So I had to flash back to 8.0, then take all the official updates, including 8.1 and firmware. Took about a day, but I didn't test any of the interim updates. It fixed all the locking up and reboot issues I had, but then the GPS started acting up.
Usually it means I can't trust any mapping while driving - it will just stop updating (in any app) which means I miss turns, etc. Sometimes minutes later it'll correct itself, but by then it's too late. Yes, sometimes it doesn't lock on and I end up rebooting just to get it back. After s fresh reboot it usually works for a little while. Also annoying is there's not even a notification or anything that the GPS is having issues, so unless I notice that the marker isn't moving, I won't know what turns are coming up.
Denim is Nokia only, so I don't have that. I don't know exactly what to test with the gpsinfo app. The latest interesting development is that when I was up in Canada last weekend, and had data off due to roaming, connected to Rogers, I had no problems whatsoever. GPS worked like a charm. I've yet to do any experimentation since I came back.