Ok, so.... We all know how bad the controllers are. I buy and sell vintage video games and accessories. When I started out I sold just about any joystick or any other accessory that a person would want or need. But then I quickly learned that the Atari 5200 controllers were consistantly bad. Someone would buy a working 5200 controller from me and then about a week or so later complain that the item did not work properly any more. After some research, I soon realized that this is likely going to be the problem with this item every time I sell one. So I stopped. I still have nearly 20 of these controllers and few actually work properly. Who knows how long they will actually work.
I guess that the main problem is basically the way that they were made. It has been my experience that the plastic pad inside of the controller that carries the signal to the motherboard seems to corrode and end up becomming the main reason that the buttons or numbers end up not working after some time. You can get new guts for the controllers which will likely fix them... but they are not super easy to install. Not too bad of a small project if you are handy with this kind of thing. Moreless; the new parts for the controllers seem to be a better quality of material than what was availible at the time that the 5200 was released. But that is just my humble opinion.