Originally posted by wharvey Can you give some details of this known issue?
There are a few threads; symptoms seem to vary a bit (overexposed, underexposed, ...). Do a search for K30 or K50 and aperture. One might be
https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/229294-k...e-problem.html
Looking through viewfinder and having a dark view indicates that the lens is closed down. This is the normal situation if the lens is not mounted on the camera, but when mounted on the camera it should be open till you take the shot. A closed down aperture also means that there is not enough light getting to the AF sensor, so the camera will have problems with autofocus.
Thinking about it, maybe the aperture lever of your lens is bent and not activated when the lens is on the camera.
In my opinion it will not be a sticky mirror; in that case LV would not give the problem (and I understand from your first post that it gives the problem as well). But you can check by removing the lens and looking into the camera; the mirror should be under a 45 degree angle.
And the shutter can be excluded as it happens before a photo is taken.