They process a LOT of film there. It's North Coast Photo Services, they're my local, and usually very good. They did seem to have an idea what was up, I'm just trying to understand it more.
Whoops! When I said that Kodak doesn't make film that's hard to process, I didn't figure on a "dip-and-dunk processor, which is what North Coast Photo uses, per their website.
I should start out by saying that I have no direct experience with such machines. That said, and I appreciate that many people seem to think they are the "gold standard," I most definitely do not. Certainly they are adaptable, and can easily handle different film sizes, but... I don't see how you can get strong agitation (it would blow the film around in the tank), you can't use squeegees (to strip excess liquid off the film), and you can't get an instant, well-controlled immersion into the bleach (without agitation or a squeegee the film may carry in a laminar layer of developer). Offhand my guess is that at least one of these explain where your streaking is coming from. And presumably the 800 film is worse cuz of the heavier silver loading.
So it may well be that North Coast really doesn't have any control over the streaking. But it also MIGHT be that their bleach is deficient, as a contributing factor. Easiest way for them to do this is to measure pH and specific gravity, assuming they have the capability. (I assume that anyone operating several dip-and-dunk machines is savvy enough to do this.) Aim values in Kodak CIS-61 (whoops, web site says they use Fuji chems, so get specs from Fuji). It's also possible that their bleach is also not aerated enough, but this seems unlikely to cause streaking. At any rate, inadequately aerated bleach would almost certainly show up on their "process control strips."
Fwiw my experience includes being the QC manager in the main lab of a large studio chain. We ran around 5 or 6 thousand gallons of replenishers every day. Primarily for paper processing; in the case of C-41 film we ran "only" several miles of film daily. My department oversaw all the chem mix results (mix operators were from a different department). But we did the chemical analyses and made mix sheets for bleach and blix regeneration, and cleared the completed mixes. (Note that my personal experience was on earlier versions of C-41 bleach, but the principles are still the same.) We oversaw the process control on all of the processors, running around 40 to 50 control strips every day, plus pH and specific gravity screening of processor chems every day. Anyway, anything went wrong, chemical or processor related, we made sure it got solved. So I'm just saying that I'm not a rookie at dealing with process problems.
Anyway, my wild guess is that, unless there is a bleach deficiency, your issue is likely an artifact of the high speed film being used in a dip-and-dunk type machine. You might, just for fun, ask the lab if Kodak condones the use of dip-and-dunk machines (I don't see any such specific reference in Kodak's Z-131). They're most likely gonna know more about it than I do - remember, I'm just making guesses.
Best of luck in your endeavors.