The problem I am having seems to be an issue with GSX not recognizing a particular aircraft properly. The aircraft in question is the PMDG 737-700NGX, specifically, the model with winglets (the non-winglet model has no issues).
When requesting boarding (or any action that causes the support vehicles to appear), GSX automatically spawns cargo loaders instead of belt conveyors. I have tried setting up the gate to only spawn conveyors, which does its job; but the conveyors do not attach to the cargo doors, instead raising their booms up to somewhere on the upper deck.
If I let the cargo loaders load/unload the aircraft, they use the medium, trapezoid-shaped containers and load/unload them from the upper deck of the aircraft.
This problem started a little while after I purchased GSX, and the aircraft used to work just fine, with the exception of catering service, which did not recognize the right side rear service door. Unfortunately I do not remember after which update the aircraft went haywire.
Thanks in advance for your help.