By default (if it's not manually set on a parking), the Marhsaller distance (and the decision to show it on a ladder or not) is based on the airplane Eyepoint, but it's not something in the GSX airplane profile, it's read directly from the simulator.
Are you sure the Longituded worked before? Maybe the eyepoint changed in one of the updates, we'll check this because, even if you can't edit, we have a way to override the airplane eyepoint in the GSX database, since we found some cases of airplanes with the eyepoint set wrong.