Finding people to count the votes
I agree with the previous posts. I'm also opposed to the use for voting of anything that can't be understood at a glance by every single voter.
I remember hearing on France Info, a few years ago for local elections, the mayor of La Rochelle (one of the first cities to use machines): he said that he did not understand how it worked, but he had a technician who did. So in that city, only one person actually had an idea of the way the system was rigged...
But there is also a real issue here: the lack of interest of voters in the actual counting. I've been volunteering to count the votes for every election in the last 5 years. In my place, for what, maybe 15000 registered voters, there are always enough, but not that many, about a dozen.
There are voting booths where there are not enough volunteers, and that is a real issue. If nobody's there, then the use of machines seems to be the only choice.