Small problem with my new/used Nikon F100. Overall, it's in great shape and works well. While shooting my first roll, the Dynamic AF dial (in the door) basically just fell out. I had been using the control, and it worked fine. Now, if I replace the button, it stays loosely in place but can easily be worked out with a sticky finger or just over time. It moves physically between the two settings, but moves past the left setting when it gets loose. But it won't change the setting no matter how I manipulate it. It's stuck in the multiple sensor mode. It's such a tiny piece, I can't tell if something's broken or it just came unglued. Thoughts?