This is not a bug, I don't know that Apple ever confirmed to anyone that this is a software bug that can be fixed by an upgrade.
I finally found a solution after months of talking to different levels of Apple support to no avail. I was going to throw my phone away when I decided to do the only thing left for me to do: replace the GPS antenna (the flex cable) by following the iFixit instructions. While I was at it I also replaced the Wifi antenna. $15 for the repair kit and the parts + 3 hours of my time and my phone is fixed! And you can believe me when I tell you that I have spent at least 20 hours talking to Apple, searching the web, testing, installing, resetting my phone, all for nothing.
It's just a hardware issue that was maybe be caused by the upgrade which could in some way make the hardware fry, or it's just all a coincidence.
What I know for sure is that my problem is gone since weeks now, not a single drop in GPS connection.
So this is my advice: cut your loss and change the hardware yourself. It's not for the faint of heart but if you have a steady hand and follow the instructions to the t then you will be fine. You only need to unscrew and screw but the screws are tiny. You can also ask a repair shop to do it for you but I would not trust all of them.
Of course I can't be 100% certain that it's going to work for you but it solved this symptom for me: iPhone 6 with no satellite connections since upgrading to iOS11.
All the best.
iFixit instructions