I used to have the A7V8X. I had the same issue as you.
I noticed this problem was a little better on some BIOS versions, but none of them really fixed it.
I found the only way to get it right sometimes was to change the voltage in the bios, reset, then set it back to the voltage you want.
After a little while it would reset to something else, however.
Very poor board in this regard IMO.