I found the issue with the BSOD for gen 1 Corsair Ones - it's Corsair Link. It utilizes a CPU-Z driver that produces a page error during the Win 10 2004 update. If you've been getting "cpuz141_x64.sys PAGE_FAULT_IN_NONPAGED_AREA" error on your BSOD, like I did, then do the following:
Uninstall Corsair Link including the config files. In fact, uninstall all 3rd party HW monitoring software. *I know deleting CL is a risk for heating but just don't game without it*
Run the Win 10 2004 update. It worked for me and pushed me thru the 80% install barrier during the 3rd reboot. Then reinstall Corsair Link for your Gen 1 Corsair One.