If the number of tags for 503CW on original_ann's Flickr site is relevant, that's the camera we're talking about. In which case, the shutter is a leaf one and won't be causing this. But the camera's body shutter, or Auxilliary Shutter as Hasselblad call it, is in two halfs which meet in the middle of the frame so I'm sure the cause is the body shutter closing early.
What could cause that, I don't know.