As explained so many times, the problem of disappearing objects it's a very well known limitation in MSFS, which will start to break up and remove things, if the overall maximum number of objects is reached.
While it's very difficult to reach this limit with just GSX alone, and in fact nobody ever had it this before several popular AI traffic product has been released in the past months, when you add an AI traffic product to a previously working GSX, if you don't act on the AI settings to keep the overall number under control, it's way easier to run into this problem.
What you can do from GSX side, is disable "Ground Clutter" in the Config panel, and run an update, to install a more lightweight version of the GSX jetway replacement files which will contain the same number of objects ( just jetways and nothing else ) compared to the files they replaced. This will work only at default airports where jetways has been replaced by GSX though.
But the most effective change is, of course, acting on the AI traffic program itself, which means limiting the maximum number of AI created.
In FS Traffic, you can reduce the number of object A LOT, by disabling Ground Services for AI in the FS Traffic configurator. Since a serviced AI can add up to 10 ground vehicles, with hundreds of AI visible at dense airport, you can easily surpass the maximum number of Simobjects ( officially documented as 1000 ), without even calling GSX for your airplane.
Note that, jetways DO count towards the limit and, on some sceneries like KORD, KLAX, EGLL, LFPG, etc, you can have 150-200 object already taken as just jetways so, it's clear you need to keep your AI under control, otherwise it would be impossible to use that airport, even without adding GSX.
