That's a firmware bug, it does nothing to your actual hashrate. I've got the same thing on my poorest performing b29, the update to the public d9 firmware runs visual autotune in a loop too.
Phew...btw, are you having fluctuations of the hashrate on the pool end as well...mine fluctuates from 3 TH/s to 0.9 TH/s?
This is standard fluctuation. Average is what counts - these all have appeared to hash a little below spec (1.9-2.0 avg) poolside.