What you saw:
HFT Alert picked up the High Quote Counts:
What happened in the blink of an eye (h/t @BadAlgo):
ECYT 1 second interval chart. Chart shows 17 minutes of data.
The green arrow points to where the wild price oscillation occurred. The NBBO is plotted in black for a normal market, yellow if bid equals ask and red if bid is greater than ask.
ECYT 25 millisecond chart. Chart shows 26 seconds of data.
At this resolutiuon, we can see the wild oscillation.
ECYT 5 millisecond chart. Chart shows 5 seconds of data.
Note the quote rate exceeds 10,000/second when the NBBO is crossed during the first drop (red shading).