It was going a bit haywire for me at the start of this week, in addition to constant lag when trying to start the app, but it's been getting a bit better. I would imagine the over-abundance of lure modules might have caused the lag for me, not sure about the GPS drift, though. Hopefully, this becomes less of an issue with the next update.
GamePress
Is the GPS going nuts for everyone today?
I either get a GPS not found and it looks as if I'm in the middle of nowhere, or I get sent to the highway nearby several times, and it takes several restarts until it puts my character over my home. Also, the Gym bug where the character forgets to walk away is back again.