Voters said the final voting submission page failed to reflect their intended vote, saying their vote was "flipped" to a different candidate, News 19 television reported.
Richland County Elections Director Rokey Suleman said the problems were caused by a calibration issue with the county's aging voting machines, according to the report.
Suleman told the TV station that if touchscreens were calibrated incorrectly, they could make unintended selections, adding that voters should carefully review the final selection page before casting their ballot.
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He added that he hopes new voting equipment in place before the next general election in 2020, the report said. Technicians told News 19 that it is typical for voting machines to get recalibrated two to three times on Election Day.