Vysk,
Given the unconventional nature of the M4-P's film path and back, if there is any light leaking from the rear, it would by necessity also be exposing portions of the film outside of the frame.
My money is on the first curtain having an alignment issue. If Jordan is like most photographers, or if he uses a winder, the film spends more time behind the first curtain than the second. Just a hunch.