I have an old film Canon ftb. It was working fine but suddenly after taking a picture, the shutter fails to "spring back" and the viewfinder remains black. For a while I could give the camera a little knock and it would spring back. I can also loosen the lens a little and it springs back.
If I shoot without the lens on, it springs back no problem. So it's something to do with the lens.
What's happening here? Is it a lens or camera setting – something I did? Or is it just broken/needs cleaning? I can't seem to search the right terms to bring up this problem on an older film camera.