I have no clue what happened. I was out shooting when all of the sudden, the aperture ring became difficult to turn. So I popped off the lens and put it back on to realize that the pin on the prism would not drop into the notch on the prong. Somehow, something in the prism had become bent or something and the pin was now a few more mm away from the body than it was before, and so it won't drop into the notch. Suggestions/help please?