Then you did not downgrade with a full version and I honestly have no idea how you could have possibly gotten to that state. I will try again with the factory firmware on my own in a few minutes just to verify, however.

http://releases.broked.net/antminer-z9-mini-201805262047-500m.tar.gz

That is the original batch1 factory firmware.

I know for a fact that the factory firmware flashes cleanly

I tested very possible combination of upgrade/downgrade/with and without saving configuration.

Please flash the factory image again, uncheck 'save configuration'.

Thank you,

Jason