A NY State election board has found that overheating is the culprit in the case of electronic voting machines that failed to count up to 30 percent of votes in the Bronx:

“There’s some kind of defect in these machines that when they overheat they can create what they’re calling phantom votes,” said Larry Norden, a deputy director with the Brennan Center. “That could mean that if the person hasn’t voted in a contest, they could have a vote attributed to them that they never intended to cast. In the case of these voters in the South Bronx what it meant was that they actually meant to vote for somebody and the machine was adding votes in those contests because it had overheated.”

Among the recommendations (aside from getting better machines): Let them warm up for a while before anyone tries to vote on them.