So far as I can tell what you are describing is normal iGO behavior. When you save a route all that is saved is the start point, end point, and waypoints. When you load a saved route iGO recalculates it based on whatever parameters (fast, easy, motorways, tolls etc) are currently set in your device.
If you need to force a particular route you need to add lots of waypoints. If you choose this option I suggest you add
to sys.txt. This means a waypoint is considered reached when you pass within 1000m of it and helps prevent the programme routing you to pedestrian-only squares and the like.
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