So this isn’t in all my photos only some, I Use a Pentax super A1. The bottom half of the photo sometimes comes out as nothing. This is annoying and unpredictable. I have read that It may be the shutter, so would using it at a slower shutter speed maybe help? I usually adjust apature manually and let the camera decide the shutter speed. Could I maybe not go quicker than 250? I just cant remember which shuttter speed the photos that came out okay were taken at/#.
The example photo appears to be the result of a malfunctioning shutter mechanism. It most likely need to be replaced. If you camera is not worth what a shutter replacement would cost, then it's time to consider a new (or different used) camera.