elekm is right and his response is a good direction for someone with a bit of experience doing repairs. Sometimes when winding, the gears inside the cameras, or outside next to the shutter will slip out. if you rack out the focus to the closest focus setting you will be able to see the teeth where the geared wheel rests on. If you remove one of the screws that hold the assembly down, and loosen the other(this is a tight one by the lid), you can decouple the shutter from the winder lever assembly, clean the shutter, and realign the gears. When the gears are not aligned correctly, winding may stop too soon and not cock the shutter, or it may go forward too much and have the lever not return. Never put force on these cameras as you can easily strip the teeth off the cocking rack of other gears making it costly to repair. Microtools sells the cocking rack for $25usd. You can check your cocking rack by removing the top plate too(really easy to do as well, just a few screws). access to the shutter is super easy, as the cameras were designed to swap front elements, there is a red indicator you can turn to and remove the lens.