I have a Canon AE-1P. I have not used it for a while. Recently I found the shutter does not work any more. When the shutter released, the mirror is locked at upper possition until you wind the film advance lever again. And the all the shutter speeds seem the same(looked like the second curtain follows the first immediately. but I can see some light goes through). And sometimes the shutter release button has to be pressed the second time to fire. Anyone know what's wrong. I appreciate any assistance.