According to this AP report, “Announcement of the results was delayed for 90 minutes because a hand count was required on one of the 18 machines” and “Supporters of Paul had sought to block voting, arguing that vote-counting machines had fundamental weaknesses, but a federal judge refused to grant an injunction on Friday. The matter was appealed to the U.S. Court of Appeals for the 8th Circuit, which on Saturday upheld the ruling, said Matt McDermott, attorney for the Republican Party of Iowa.”
More details when I know them.