I have been having this problem as well since the update to version 3.7.4. Im am running MSFS2024.
GSX lets me choose a gate (the "select from map" option is great, by the way!), and as I arrive there, all the vehicles are in place and the marshaller or VDGS works fine to park the aircraft.
But as soon as the engines are off and I request to operate the jetway via the GSX menu, I get a "bad jetway data" error message (I only see the upper half of it). If I restart couatl and then operate the jetway, it works fine.