Why does the SPY chart have weird spikes while ES does not?

There is lots of bad prints or late prints which cause you to have spikes in your charts even though the price never traded there. The spikes didnt actually happen.
 
I'm looking at stockcharts.com intraday - there was a spike down to 122.5 on 7/29 near the close while the lowest price per yahoo for the 7/28,29 was 123.42.

This same spike is on other charts too. Similar weird spike down on 7/15.

So someone made a small trade at 122.5 and ran it thru late in the day?
 
I have been backtesting some systems back to 2006 and see these spikes in the spy back then as well , it may have to do with the fact that the spy can be traded on multiple ECN's ...
 
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