Seems to be that I also have to power off/on the screen after a reboot? Tested this and rebooted a couple of times after saving the settings in the BIOS and all worked fine (even with 32GB Vengeance).
But then I switched to the HDMI port to test itand all I got is flickering screen. So my guess is...BAD HDMI port!
I had my old 850W Coolermaster PSU running this at the very beginning, but all I ended up with auto-reboot after auto-reboot, so I switched to my 150W Pico-PSU using DP-port.
Not going to use that HDMI port again.
Had to clear the BIOS and reboot, all fine again!
I have attached a (bootable, as it contains truenas) SSD drive, BIOS sees it, but I can't seem to set is a boot-drive? As after reboot, the system ends backup in the BIOS.