That's the one im using in all my miners, tried smiths firmware too. nicehash firmware too.
I have the exact same "problem" i decided to just ignore it as overall its 2-3ghs loss;
I posted about this in several places and got a few replies but nothing helpful. I can sum it up to people posting the same 101 troubleshooting suggestions and a handful of others saying they have the same problem.
It still happen once or twice a day. Its the top blade if you look at it in the webserver in miner status.
It look like a sharp dip in the pool's graph everytime;

Typically only last 2-3 minutes.
Edit: My S5 is batch 7 (used from bitmain) on the latest PCB.