How do you revert a z9 mini from Fuddware 2.3 back to Bitmain  antminer-z9-mini-201805262047-500m.tar.gz?  (batch 1 firmware)

When I load Bitmain firmware, the miners are complaining

"Invalid system and miner configuration file. Edit manually or reset to default."

I have tried to reset to defaults but Bitmain code still complains.

Any advice on this?

Thanks,

Tom