Hi, using both an API call and also using the developer test URL (https://developer.mapquest.com/documentation/samples/directions/v2/route/) - the route between
From: 1125 South Road, St Marys,SA,Australia
To: 4 Majors Road,O'Halloran Hill,SA,Australia
is routing via Seacombe Road instead of continuing straight on Main south Road and then turning right onto Majors Road.
I have tried both Fastest and Shortest route options. You can see the image of the result here. --> https://www.dropbox.com/s/1j8exubjlz4ct62/Route.jpg?dl=0
PS. the red route is what I would expect.