Firstly, I have processed and printed several rolls of colour negative film recently (although not Portra 800), exposed with my Bronica SQ-B, and not come across the illustrated density marks once. I've not yet scanned the film in to check whether it is on the negative itself, but I do suspect an optical issue as the density mark has appeared on black & white film as well, but again only the RF645 negatives. I've printed other frames from the same roll to 12x16" and not found the marks present.

Has anyone else come across this particular problem?