portatour® transfers the address to your navigation program. If your navigation app then incorrectly geocodes the address, you will be directed to a different geolocation.
If you always want to pass the geopositions of portatour® to your navigation app instead of the addresses, go to Options > Program settings. Under GPS Navigation, select Navigate to geoposition instead of Navigate to address (see Program settings).
Hint: Note that not all navigation programs support both modes. portatour® selects the other mode if necessary.