Do you maybe have a GSX.CFG file in your Simobject\Airplanes\PMDG 777F folder ? Maybe a file you downloaded a while ago, and forgot about it.
If yes, that will take precedence over the GSX internal database, and it won't be removed by the "Reset" option, because that folder is supposed to be used only by airplane developers to distribute a GSX config with their airplanes, so it's not removed (it's supposed to be correct...) with a Reset.
When in doubt, you can check the GSX airplane configuration editor: the top two text lines will tell you where the configuration data for an airplane is coming from, and which one is used by GSX at the moment.