Edmund, I have the 3.7.8 version. If you want to try it just tell me. I'll make you an image of the CD. It may help solving your problem. (Who knows, maybe the "striations" too.)
I have tried the V4 Beta 2 and I still have striations, they just move around to other places on the same images and I really hate to look at the display on my back, the banding there is so ugly. The software does clean that up -except sometimes it doesn't.
Because of the way the problems move around the images, I don't think the factory calibration is necessarily bad, I am enclined to think that the back is drifting away from its calibrated position because of some hardware problem.
As an engineer I don't think sweeping hardware issues under the table with a software fix is a reliable long-term solution. If that back has a bad condenser in there or a bad solder joint, that will eventually come back to haunt me. And Murphy's law guarantees it'll happen when the prettiest girl in the world is standing in front of my lens
I now have zero confidence in this back. At this point I think Phase should provide me with a sample of the P45+ that is clearly within spec and shoots well at 400 and 800 Iso with no strange artefacts. I paid for the VA warranty, so assuming less than 10% of the backs have an issue, Phase shouldn't consider they are losing money on a swap.