Ed I have the same "problem" with my A65 back.....but when the image processes it dissapears.
In your case it doesn't, maybe it is a firmware upgrade?
In my images it is most evident in underexposed situations.
Interesting you should talk about underexposure ...
My underexposed shots with this Phase P45+ back are often wrecked by *horizontal* stripes, but here Phase claims it is because they are underexposed .... The image above (and some others) is more entertaining because here the edge is *vertical* while the shot is well-exposed.
The thing is, these vertical and horizontal edges are very visible to me because I'm a color consultant, and I know they will be equally visible to any working photographer, but in an unenhanced image they are not visible to a "normal" person working in a camera dealership. Of course, once a file is manipulated in Photoshop, curved or sharpened, any defects jump out. Anyone who doubts this can look at the C1 screenshot above and the way it gets turned into a print.
Ric Agudelo (Ric Agu here on LL) shoots Phase and uses my Phase profiles, and he was in Paris this weekend, and he too could see the centerfold and banding issues with my back with one glance at the display.
All of this makes me very, very frustrated, because the ergonomics of the back are good, the camera works usably, the colors are wonderful, the resolution is superb, there is little grain at ISO 400, but I cannot get the hi-iso (400+) imagery I want because the back I paid for is broken