While not unexpected, this appears to be the first confirmed issue with voting machines so far today. It happened in Pennsylvania.
CBS reports:
There have been some scattered issues where voters are encountering problems.
Election judges in Clinton Township, Butler County confirmed there were issues with two of their eight automated voting machines. Most of the issues came when people tried to vote straight party ticket.
However, other said they specifically wanted to vote for Republican Donald Trump only to see their vote switched before their eyes to Democrat Hillary Clinton.
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