If it is happening at home, I wonder if there is some sort of issue with WiFi triangulation actually? What happens if you disconnect the WiFi radio (in settings / wifi; as we all know, turning it "off" in the control center in iOS 11 just disconnects you from your current connection while leaving the radio on for location purposes) and see if location stabilizes (potentially after a phone restart.)
I will say that I was seeing a similar issue with my 6s a couple of weeks ago -it was floating quite a bit, and even showing location across town at times - but I found the issue to be a Verizon Wireless home extender we have in our house. I think it was having some GPS issues of its own and getting fluctuating GPS, because when I unplugged it, location immediately improved and my phone was locating exactly right.