Throwing this out as an experiment with AI... which is getting sort of spooky.

The "powerfailstate" error after a Williams BB2 to BB3 conversion typically indicates an issue with the non-volatile memory (NVM), the power supply, or a required RAM clear procedure that was not properly executed or is failing. This error means the machine detected a power fluctuation or failure that corrupted some settings, or the new board's NVM is in an undefined state.
A RAM clear is a crucial step when swapping major components like a CPU board during a conversion. The new BB3 board needs its NVM reset to factory defaults and properly configured for its new environment.