This has been already discussed and answered so many times already, and it's not obviously a GSX problem or "bug". There's an hard limit on the number of objects in a scene, after which the simulator will start to randomly remove objects, and stop to accept commands to create new ones.
Nobody had this problem before AI products using AI Injection came out.
Obviously, is nobody's fault, not GSX, not the AI injectors. Not a single add-on is to "blame", but if you use them all at the same time, you can reach the limit.
if you are on a large airport that might already have a large number of objects on its own, add GSX with its own objects, and then add AI with too high injection settings, or just too high settings (even without injection), the max number of objects limitation is being hit, and nobody can do anything about it so please, it would be best if you would at least understand this is a simulator limitation, NOT a "GSX bug". Fact you solved it by uninstalling GSX doesn't mean it's GSX's fault: you would achieved the same result by uninstalling the AI product, or just lover the AI settings.
There IS one thing you can do in GSX, and is Disabling the "Extra Ground Clutter" option in the GSX Config panel, then run an Update.
This will install a lightweight version of the GSX jetway replacement files, which doesn't contain extra objects like traffic cones, FOD bins, toolbars. It contains just the jetway, meaning GSX wouldn't increase the number of object compared to how the scenery was by default. However, this only matters at airports that has their jetways replaced by GSX, which should be only default airports.
There's a post discussing this problem on the official MSFS forum:
https://forums.flightsimulator.com/t/arrival-airports-traffic-and-fps-have-disappeared/552363/25Please pay attention at what the poster is saying ( he opened the thread ):
I actually had this happen only using AIG and not GSX.
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There are so many objects at the airport, it must have reached the limit with only the traffic added
That's clearly proves GSX is not the problem, the problem is the overall limit of objects being reached, no matter how.