It depends if that cart has been flagged as a Ground Vehicle or not. Maybe it's not, because it's being pulled by something else, so it doesn't need to have a proper ground vehicle physic since it's always pulled by a real ground vehicle, so maybe its category is not GroundVehicle.
We had to change this, because in previous versions, we searched for ALL objects categories around the user, because using the "All" method, didn't include Jetways. A bug we reported 3 years ago, which seems to have been fixed in SU3. Assuming this bug would never been fixed, we just removed every object inside the parking radius, with some exceptions to protects 3rd party objects like PMDG or other things supplied with the airplane or airport, because we knew jetways would never been included in the list we get from Simconnect.
This worked fine but, in SU3 they fixed that bug after 3 years, so now jetways ARE included in the list of objects around you. So we had to update GSX in a way that ONLY AI airplanes or GroundVehicles are checked for removal, otherwise the jetway would disappear when calling GSX, and there's no way to reliably detect if something it's a jetway, because it's listed as a StaticObject.
So, the fix required to prevent jetways to be removed when calling GSX, has made GSX unable to remove anything that is not flagged as a GroundVehicle or an AI airplane.
