GSX2 tries to open the doors automatically (i.e., without me opening the doors via the FMS) but the doors get caught in a loop where they open partially and the close and the repeats.
As explained so many times on the forum, GSX NEVER tries to open or close the airplane doors automatically. Some airplanes do that from their code, and there are 3rd party products that do that too, interacting with GSX, so you might be mislead into thinking it's GSX, just because you see the door opens/close in reaction to something you do with GSX, but it's not GSX, it's the 3rd party product you use that reads what GSX is doing and opens/close doors on the airplane. If not the airplane itself.
Some 3rd party add-on that do this are MCE++ or FS Captain, if you use any of these, you should check their documentation or their support to know how to use them correctly.