Ender 3: Lost communication with MCU 'mcu'

I admit I don’t know what host the Ender3 uses (just that it is nominally Open Src)
Its just that my Voron always works from a power on. However, if you make any changes such as change a config and do Firmware Restart (it sometimes dies until re-power) or hit the software Red Button and select Reboot (it never works until re-power)
And I definitely have the buggy Bullseye.
I haven’t been game to complete the upgrade because of errors as listed in: