I have purchased a Grafmatic 45 film holder. Everything is straight, all of the septums are straight and hold film well, everything opens and shuts exactly as it should, except for one thing. The darkslide lock, doesn't turn to lock the darkslide! Well it turns a little bit and just covers a poofteenth of the darkslide, stopping it from coming out. But I cannot get it to swing right around so the red dot shows. Does anyone know if I can just undo the screw holding it a bit, or will things fly apart? I haven't used one of these for close to 20 years and it took me a bit of fiddling to get the memory all together. Mick.