I see. Is that something that I should have known, or is it trial-and-error?
Your screenshot shows a default airport, so you were not supposed to disable GSX jetways, because they work there.
The problem in your screenshot doesn't have anything to do with GSX, and it's not solved by disabling GSX jetways either (because that's a default airport), and your problem doesn't even affect jetways, which are in their correct position.
The problem is the static bridge that hasn't been extended to reach the jetway root, and this is a very well known bug that has been reported to MS years ago, before GSX even came out, and happens with default airports with default jetways with no GSX installed, and nothing in GSX can change or fix that, since it was never fixed.