RN104 - "USB Boot Failed!" on Display, USB Recovery Drive not Working

Hi, my RN104 was successfully updated to FW 6.10.4 when the FW became available.  It's functioned fine until now.  I normally have it powered off and I know it does power on by itself occasionally (about every 2-3 weeks).  I came into the room to find the unit powered on, backup button light and power button light both flashing rapidly, and the display reading "Boot from USB Failed!"  The only way to power it off is by removing the power cord (forced shutdown) - the power button has no effect.  When I reattach the power cord, the unit immediately powers on with the same flasing lights and message on the screen.  I'm unable to access/get into the Boot Menu via the RESET button method, even if I press and hold in the RESET button and reattach the power cord.  I've also attempted to build and use a USB Recovery Tool (kb29952) and haven't had success with it. 

The first one (32 GB USB drive) is sensed and appears to perform a recovery...it finishes and powers off in under 1 minute after the "ReadyNAS USB Recovery" message appears on the screen.  Powering it back on with the power button returns it to the original failure state (flashing lights and failure message). 

The second one (2 GB USB drive) doesn't seem to boot - the display never changes from "Boot from USB" no matter how long I depress the Backup button. 

The 3rd one (8 GB USB drive) is sensed, appears to perform a recovery, and powers the unit off in under 1 minute, just like the first USB drive...powering the unit back on returns the same failure (flashing lights and message).  The 1st and 3rd USB drives were formatted as FAT32, the 2nd one was already formatted as FAT.  I went back, reformatted the 2nd USB drive as FAT32, rebuilt it as a USB Recovery Drive, and tried again...same as before, it doesn't appear to be read and the display remains at "Boot from USB".  I'm also unable to access the Boot Menu after using any of the 3 USB drives and powering the unit back on while holding in the RESET button. 

It appears the ReadyNAS hardware is failed but I wanted to see if anyone else has any suggestions on what to try.  The ReadyNAS unit is connected to a Windows PC running Windows 10 Pro x64 OS, version 20H2.  I do have access to a Windows 10 PC running Windows 10 Pro x86 OS, version 20H2.  I may try building the USB Recovery drives on it later this week.

Thanks for your time and suggestions!