Out of curiosity, is the example image the full frame or is it a crop?
My first thought was that I was looking at the camera strap dangling in front of the lens and part of the photographer's sleeve on the right margin. Assuming that is not the case
, it is probably some sort of mechanical issue.
As noted above, I also suspect an issue with the shutter, though it is hard to say which curtain is at fault without knowing the orientation of the camera (top-right vs. top-left). Either way, one of the two curtains (probably the follower) appears to be "stuttering". It also appears that one of the curtains is partially jammed at the start/end of its travel.
Issues with a vertical metal shutter are not something that you want to fiddle with yourself. They are robust in use, but have a delicate mechanism that may be easily damaged. A good repair technician should be consulted.
Steve