If the airplane for any reason ( scenery, ground, collision with ground, collision with objects, etc. ) has a sudden movement during pushback, GSX will automatically abort the pushback, as an obvious safety measure in case something goes wrong, you retake control of the airplane and want to just continue taxiing and take off, so we cancel every service and every GSX vehicle, so you won't be taxiing with a tug attached and possibly other GSX objects in the way.
If this happens, you'll see the regular parking selection menu, as if you just restarted.