Running two macs (Macbook pro and Mac mini). Both running OS X 10.11.6 and the latest version of Prey.
Installed Prey yesterday and location information for both machines was pretty accurate. Later got messages that machines left area (which they didn't), and are being geo-located in the next town over (of which they're not... I'm writing this from one of them now). WIFI is turned on on both, Apple Maps can detect the location pretty close, as can google maps website, but not Prey.
Uninstalled Prey and removed from the console, reinstalled and rebooted on both machines, both still showing up at same bad address next town over. Changed wifi network I was connected to (ISP wide area wifi), then updated location and the location changed to a town that's a 30 minute drive away. Changed back to my wifi and now I'm back to next town over. Not sure why WIFI geo-location is so poor now??