[St Evelyn]

In the Mk1 XC60 this would occur if you moved the map around using the number keys underneath. If you then press the Nav button it would 'reset' you to your default settings and the map would move with the car / arrow. That said, turning the system off and on again, such as would happen when locking the car, would perform the same function, but your post suggests this is an ongoing problem. I'm not aware of any other settings that can be changed to create this scenario.