Hello, this is a workaround you can use. The file is attached below, and place it in your \Final Approach Simulations\Caribbean Airports MKJS\scenery folder, replacing the existing file. This should allow GSX to display jetways in those locations where static aircraft are present. You may possibly need to edit the jetway liveries in the GSX airport editor, as they seem to be random each time the airport is loaded. Since it's not a perfect solution yet, it won't be included in an update when you install the scenery, but you can always refer back to this thread for the custom file.
GSX completely removes the jetways with no associated gate, which is the case for the gates occupied by static aircraft. To work around this, this file adds gates where the static aircraft are positioned. They are labeled as "RAMP MIL COMBAT" parking, so be sure not to select any of those locations when starting at MKJS. Most AI traffic programs shouldn't have aircraft spawning in "RAMP MIL COMBAT" gates, but that could be a possibility if they are not programed to avoid those spots, which would result in aircraft spawning on top of static aircraft.