The problem doesn't have anything to do with GSX, it's the very well known error 99:
Error: exception JETWAY_DATA in call RequestJetwayData param #99 'KOKC'
Which is an internal Simconnect error, and we noticed it's more likely to happen:
1) When the maximum number of Simobjects in the sim is reached, usually linked to using AI traffic and/or very detailed airports.
2) When some add-ons make too many Simconnect calls while GSX is asking for jetway, so Simconnect just can't keep up with all the data.
Problem #1 can only be fixed by lowering the AI density and, from GSX side, reduce the Passenger density but, of course, if this happens ever before passengers are show, it means the problem was already there even before GSX added any objects.
Problem #2, if happens only with certain 3rd party airplanes, it's usually fixed by going back to the Main menu, and entering the airport again.
