I was going through the same issue, and tried to disable fastboot, enable/disable xhce handoff, enable/disable legacy USB support, etc. Nothing to prevent my USB boot drive to sometimes unrecognised from the BIOS, or booted to unraid just to then having errors (dev/sda check return "device descriptor read/64 error"). You can try plugging your USB boot drive into the 2.0 port, AND that is the only USB 2.0 port active on the motherboard. I moved the USB cable connected to my UPS, keyboard and mouse to USB 3.0 and the issue went away for me after a few reboots and a cold startup. Samsung Bar Plus USB 3.0 & Asus B550-F Gaming Wifi II motherboard.