Sensitive stock-brokers make the flash rises and flash declines is my theory! If they sit there and are incredibly alert to everything with their companies/portfolio, they may act a bit hot-headed and this _can_ cause these flash changes, I think!
In addition, due to an increasing use of programmed "robots", these robots can aggregate with these effects as we see!
This is a comment over the recent months of these flash changes with the NYSE/Dow Jones Stock Market of New York. You can add some other, but to add NASDAQ in this manner may be considered strange for a number of reasons, part. the data-set, that the behaviour displayed by NYSE isn't seen so readily with the NASDAQ.