Hello, I'd like to ask for HUGE help. Recently I got interested in old Film cameras, and as my grandpa has an Zenit-E, (It was in our home anyways), i fiddled around with it trying to see how it works. I wanted to change ISO and accidentally broke it somehow. I got it working again (Again, somehow I have no idea how). And now its broken again, the curtain is INCREDIBLY stiff and doesn't want to move at all. When I turn the thing to get another picture, it turns but the ISO wheel doesn't, when I click nothing happens. Yes I've tried turning to screw under the camera but that didn't work.