Hi all! I pulled out my backup F2 for the fireworks on the 4th of July and came across an issue that I have not had before. When I set my Shutter speed to 1, 1/2, or 1/4 the curtain opens and the mirror lifts but then it stops. When I try to advance the mirror will not lower and I have to reset it by hand. The Shutter works perfectly at all other settings including Bulb. Any advice would be much appreciated. I know I can just avoid these shutter speeds but if I could fix them I would love to get these beauty back in full working order. Thanks!