It seems that I have this problem whenever I park underground. I suppose the gps signal is too weak there. But I never had this problem on older firmware. Only started occuring on 8.1
I have the problem when I am underground as well. The iphone app won't give me a location for the car now that it is parked in an underground garage (or gives me the 0,0 location in Africa). The car shows a location on the nav screen, but it may be off. When I was driving through Holland Tunnel in New York a few days ago, the GPS thought that I was on a surface street in Manhattan, even when I was in the middle of the tunnel, under the river. Both in the garage and in the tunnel Google Maps on my iphone shows the correct location (and so does the Tesla app for my location, but not for the car's location). On the way back, the car GPS worked correctly in the tunnel and communicated the correct location to the app, but then it failed when parked underground, in the same spot that had always worked for months.
I never had a problem before 8.1 so my guess is that what I am experiencing is a firmware issue for the way the car deals with location fixing in the absence of a good GPS signal.
X90D, AP2/FSD, currently on 17.11.10.