Despite what the VIX index may be telling you the image is clear that the sell offs are getting relatively harder and faster. As volatility cycles increase in amplitude and frequency we see an increasing amount of "one in a million years" events happening weekly. Between flash crashing, system bugs, pricing errors or whatever else it needs to be called liquidity is not there when its needed and its leaves firesales as the outcome.
I expect to see increasingly violent moves in the S&P 500 as the business cycle comes to an end. Whilst circuit breakers may be in place to 'physically' stop these sell offs, instead the pressure and desperation shall build and cause knock on effects elsewhere in other securities.