You could try excluding the jetway replacement, as it already has custom jetways?
In the FSDT Installer in the GSX line, there's a 'Config' button. Use that and then select the EDDK code and hit 'Exclude'.
I'm not super experienced with GSX but think that's what you need to do e.g. exclude all custom airports that you don't want GSX to replace the jetway with. (The installer also links the Manual, with the jetways bit on Page 7 onwards).