the problem with paper ballots, is not that the vote itself was or was not cast, but it must be compared to a person.. how can a software do that?
Many cases there were, where people voted with the willy-nilly sent out "mail-in" ballots, and then voted in person also.
Today a local fellow treated several of we veterans to breakfast. In the discussion, one of the vets said that at a nearby voting place, when folks went to vote, they were Told they had voted already ! Actually what happened was that somebody voted in their place!
Another, getting ready to go to Florida for the winter, claimed he could have voted twice and got away with it. Others in the same situation agreed, the only thing that stopped them, was truth, and a sense of honor.