For those of you using Godox triggers with the EOS R, I have a solid workaround with only two downsides. First, you loose HSS. Second, you loose (some of) the simulated exposure in the EVF (a positive in some situations).
Whatever is causing the issue of resetting the ISO to AUTO (1600) is coming through from the four non-trigger pins in the hotshoe. By covering those pins, the bug goes away.
I've experimented with two solutions. First, you could cover the rear four pins by placing a thin sheet of plastic between the hotshoe and the trigger. Or, if you are paranoid about that like I am, use any cheap eTTL passthrough shoe and place the plastic between the upper hotshoe and Godox trigger foot.
Or, buy something like this: https://www.amazon.ca/gp/product/B004G47I7O/
That makes the Auto ISO issue go away.
It also makes the wake-up feature go away. So you have to set the trigger to stay awake. I get about 300+ images before I need to replace the enloops (rechargeable AA's) in mine.
The camera also looses the Exposure Preview function if ambient is too low, because the EOS R cannot detect the trigger. In studio, I don't like that so I turn the exposure preview function off and the EVF then shows me a consistently well lit screen for composing the image. But, and here is the great part. When mixing flash with ambient, you can do what I truly deeply wish had have been possible from the very beginning - you can see the Exposure Preview for the ambient, while also using a trigger. So, want to see where the ambient shadows fall so you know where your subject should face/pose/move? Want to tweak exposure so rim light is perfect, hair glowing, nothing clipping? NO PROBLEM! Then just add flash as needed. I cannot see how Canon overlooked this, but suspect it was because so few people would benefit. I am sure a feature like that will make it into a Pro R body.
Anyway, there's the workaround for now. When I need HSS, I'll go back to my other failsafe - I shoot with image preview on in the EVF. There's a setting so you can see the last image until you press the shutter half way. It gives me the chance to review the image for a half-second or less to confirm that the exposure isn't blown. Then I move on.
Hope this helps someone while we wait for Godox to hopefully update firmware to fix the bug...