It looks like the issue is from Google Maps API, I just tried searching "3000" on google map and it doesn't give me a location in Australia, but searching "3000 Australia" does.
TastyIgniter uses google to retrieve the coordinates from the postcode/address entered, before checking if the coordinates are within the marked areas. In this case the postcode entered does not only correspond to an address in Australia but another in Denmark (funny). Anyways, a possible solution will be to lock the search to a specific region.
Try this and let me know if it works.
Open system/tastyigniter/libraries/Location.php on line 651
Change
$url = 'https://maps.googleapis.com/maps/api/geocode/json?address=' . urlencode($temp_query) .'&sensor=false'; //encode $postcode string and construct the url query
to
$url = 'https://maps.googleapis.com/maps/api/geocode/json?address=' . urlencode($temp_query) .'&sensor=false&components=country:AU'; //encode $postcode string and construct the url query
