Recently got an e6430 with bios a A13. I wanted to downgrade to A12. Every time I do it, the process does the same thing. It has a progress bar saying it's preparing to update, but then just reboots and nothing changes. I've used DOS bootable USB, and Windows methods, neither is updating the bios. 

I tried going to A03. Tried to going A18, A20, etc. But nothing ever works. The progress bar says it's preparing, then reboots.

Is there some setting I'm missing? I don't see some sort of "allow downgrade bios" option in the bios settings list. 

Thanks.