Some traders alerted CNBC to the issue, saying it was affecting the quote for the Dow Jones Industrial Average, which traded in a flat range in about the last 50 minutes of trading. Index values may have been impacted by the processing delay, but all trades were completed appropriately, the sources said.

https://www.cnbc.com/2019/08/12/a-trading-issue-impacted-us-stock-quotes-late-in-the-day-as-dow-flatlined-into-the-close.html?mod=article_inline&mod=article_inline