Imported route (gpx) does not recognise a ferry crossing as part of the route

An imported gpx file is incorrectly interpreting a ferry crossing resulting in a U-turn halfway across the river and a diversion to the closest bridge crossing and then a return to the ferry crossing destination on the other side of the river.  A 100km diversion.  Placing waypoints at the start and finish of the ferry crossing with a straight line between the two does not resolve the problem.