I just own the GSX Basepackage and P3D v5 aswell as NO 3rd Party Developer Scenery, which means I do use the default Scenery.
I don't know why you think this is a problem or why you think it started after you updated the simulator. The problem is you don't have GSX Level 2! Without GSX Level 2, jetways at default airports will be replaced but they won't animate.
Now to the weird problem: In P3D v5.2 the Jetway did work properly without any problems and did show the animations, as they supposed to do
No, they didn't. Not without a valid license for GSX Level 2 Expansion, which you said you don't have. What you are supposed to see, when you install GSX without a valid license for GSX Level 2, that DEFAULT airports will have the jetways replaced by GSX, but they WON'T ANIMATE.
The replaced jetways will start to work ONLY if you activate a valid license for GSX Level 2 Expansion.
Now, you said you updated the sim, and I think I understand what's happening: when you update the sim, default jetways that were disabled by running the GSX installer will be re-enabled by the simulator updater. GSX obviously checks this, and will show a message in Red on the top text line, saying that, because a simulator update has been applied, you should run the GSX Control Panel to disable the default jetways again, so you won't have to reinstall GSX.
So, just run the GSX Control Panel, click the button to disable default jetways, and they'll be gone.
But of course, unless you activate a valid license for GSX Level 2 Expansion, the jetways replaced by GSX will show, but they won't animate.