I probably should have followed up on this earlier. Although I haven't yet fixed the problem, I have discovered the apparent cause of the effect after emailing Eric Hendrickson. According to him,
"In your picture, the dark line at the very edge indicates the shutter bounce system is going bad. It usually shows up on faster speeds but can progress to the slower speeds in time. What happens is the second curtain comes back into the format and blocks the light leaving that part underexposed. I can replace the bounce system for you. "
Patrick, I can't say for sure what you are seeing is due to the same problem. But it is interesting that it appears as a light stripe instead of darker as in mine. Not sure what that means!
In my case this problem started showing up
after I sent the camera in to Eric for a more generic shutter problem and some other things. Since then I have also noticed that the image spacing varies, so I may have a film advance problem too. All of this has me wondering about the overall reliability of this model. But I suppose that is a topic for another thread.