Should not surprise anybody. Doug and his crew have been pulling this on customers for years, and it's the reason I have stopped buying anything sbig/cyanogen.
My only question, and this may have already been done in this post, is there a reason to stick with zwo? Why not try another camera like FLI, then see if the problems go away. You already have the software and $$$ invested and maybe someone at the remote site will loan a camera.
Many vendors blame the hubs, and for maxim 666 that is the first excuse that they will use to get rid of you. I have the Icron powered usb hub with 150 ft of cat 6 cable, SGP and no problems. There was a noticeable improvement in going from cat 5 to cat 6.
In all fairness to maxim, version 5 worked very well. 666 has been a train wreck for many.
I used an ASI290MM-mini, ASI174MM-mini and a QHY 5-III 290 for my guide scopes and OAGs. I have had no issues at all with SGP and PHD2 related to the cameras other than when I had the USB speed at 90. This has been for over three years. I also used and ASI174MM-COOL at one point for my guidescope thinking that I would see a benifit for a cooled guide camera. This was just not the case at all. A good dark frame compenstation in PHD2 works just a well. It seems that you dont and an issue with running without the cooler. Is there some reason that you think that you need to have a cooled guide camera? I would suggest the ASI174MM-mini since it has a nice sized chip, but the ASI1600MM that you have without the cooler should be fine. Is there something I am missing here?