Sequoia was demonstrating a voting machine, and the demo screwed up. Votes were not recorded to the "paper trail", due to a setup error. Thanks in part to the paper trail, the situation was found, and corrected. The voting machine makers still want to insist the paper isn't necessary.
What kind of denial are they in? Scientists have said the best system is not even touch screen voting: it's paper ballots scanned into a computer, and producing a receipt indicating what was scanned. In other words -- go back to the old fashioned paper ballots used in the Global South, but scan them with fancy ballot scanners. You'll get instant counts.