Robinhood isn't sure what's behind its latest outage, which hit during the worst day for the Dow since 2008 and knocked out the app's fractional-share trading for most of the session

· A Robinhood spokesperson told Business Insider that Monday's outage was not related to the issues that sidelined customers for two days last week.
· The cause of the latest outage, which began shortly after trading started and plagued the app until 3:30 p.m. ET, is still unknown, according to the spokesperson.
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