A shutter problem can cause a band like problem if the shutter is sticking or jumping. That is only with a focal plane shutter and not a leaf shutter. Secondly, a flash sync problem may cause a band or one side of the exposure to be total over/underexposed but not down the middle usually. And this is across not along the length of the film.

The original post by Paul - photophorous indicated the bands line up from frame to frame and by this I took that he meant along the length of the film as opposed to across the film . . .