@blouse - I also just built out a Z390 auros pro wifi with i9 and 32gb. 970 EVO m2. Single Radeon Sapphire Pulse.
I've got one odd issue that I can reliably produce. My system freezes during large/bulk IO operations. Example. If I copy 30gb or so worth of files from a USB disk to my 970 EVO, my system will just crash part way through. No panic message or anything (I've got verbose on).
Crash also happens any time I try to do a full backup to another SSD. It typically wipes out at around 5 or 6 gigs worth of activity.
Otherwise, I can work on the system for hours on end without any issues at all. It just doesn't like big IO operations.
I tried disabling XMP. No difference.
Any ideas would be very welcome.