Maybe the OP should ask the lab how it processes B&W film?
I would put it down to uneven development as well but feel that it may be caused by aggressive agitation leading to surging through the sprocket holes.
We had a drug store recently mess up developing c-41 in a similar fashion. All the sprocket holes had streaks that were much more obvious than the one in the original post. Rolls of film exposed 20 minutes before and after came out fine, and inspection of the camera showed no problems.
I'm not saying it is your problem, but the drug-store in question used the typical machine that is supposed to be fairly fool-proof, so it is possible to get these results with an automated process.
Jim, if it would be the shutter, all my images should be wrong which were taken after this shot. But the next roll had 36 almost perfect exposures.
If you are a regular customer and it values your business then if they don't think you are about to slap a big compensation claim on them you might get an honest response to the effect that something might have gone wrong.
Worth a try. You could rely on us coming up with the right answer but neither you nor we will ever know if we have got it right.
Referring to my previous post, my theory on the film we had developed, seeing that the drug store developed two rolls and one was fine, is that either the machine jammed to an extent, or perhaps something momentarily happened with the chemical levels/flow. Just a thought.
Thanks for anybody for ideas!
I don't see any point to highlight this issue to the lab. If it's happening again, I can choose another lab anyway.
Also possible that it is a light leak through the light trap on the cassette if you wind the film right in and expose to a bright light source. This will always happen with IR film if you take the cassette out in the daylight, and the banding looks just the same...I know, I've done it!
Realize that this is not IR, but there is a slight chance this could happen?