I'm not sure which last update you are referring to, because it surely hasn't changed anything in the airplane editor and, fact that PMDG planes are not affected, should indicated it's not a GSX problem.
We haven't done any configuration of the QW787, so it's either a config you made, or one you downloaded, or one that comes with the airplane. Check in the GSX airplane configuration page where GSX is taking its data from, which might give you some clues about what's the problem.
Maybe, if PMDG planes, which comes with a pre-made configuration, are not affected, because something in your system (usually the antivirus) is preventing GSX to access its preference folder under %APPDATA%, which is only used when you made/edit an configuration.