gigabyte b450 aorus elite

In preparation for an upgrade to Windows 11, I have converted my Windows 10 boot drive (M.2 MVMe SSD) from MBR to GPT, using the mbr2gpt.exe Windows tool. I then tried to reboot into BIOS (B450 Aorus Elite, Ryzen 7 2700X), to switch to UEFI boot mode, but I cannot get to the BIOS as the machine...

After I played around with my timings on my G.Skill 3200 CL15 (and 3700X) and a few crashes I decided to go back to the default XMP profile and get back to tightening timings later. However, I can't seem to go back to the XMP I used these last couple of days because the bios reset every single...