“At the open, most markets except for the NYSE opened at 9:30, and if you’re trading an S&P ETF and 50 percent of the S&P is not open, you have some pricing challenges on your hands,” Chris Concannon, head of exchange operator BATS Global Markets, told Reuters.

Now, the SEC will have to analyze the data to try an obviate another similar occurrence during volatile trading. The rules prevented massive canceled trades that followed the flash crash, but the widespread halts may have weighed on a quick market recovery.

“We have a discrete issue in the application of the limit up/limit down circuit breakers to ETFs,” Gallagher added. “Do we need to differentiate ETFs from common stock when we look at circuit breakers? Do they operate so differently that they shouldn’t be just lumped in under the same rule?”

In the meantime, investors should not get sucked into panic selling over extreme short-term volatility. Instead, people should take a more long-term outlook.

“Markets, this is the way they work,” Gallagher said. “They fluctuate. People get scared when they see these fluctuations but this is the greatness of American capital markets.”

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Max Chen contributed to this article.