The App relies on the device to provide GPS co-ordinates from which it generates a human-readable (& NZTA compliant) Location description.
Some phones, particularly older model &/or lower spec'd ones, may have a noticeable lag when it comes to updating the location. In this situation if you simply wait a minute or so and then click the location icon to refresh things, that should update to a more accurate value.
If you continue to experience inaccurate loccations, try turning off WIFI.
Failing that send our Support Team a ticket with details about your location, your phone and anything else that you think might help us recreate the issue.