I am not an expert but what I've read is that in the Dominion system, when a Ballot Marking Device is used, it generates a QR code representing the vote in addi

I am not an expert but what I've read is that in the Dominion system, when a Ballot Marking Device is used, it generates a QR code representing the vote in addition to the human readable ballot. Next, the ballot reader machine reads the QR code, not the human readable portion. Assuming this is true, it would be simple to modify the printing software such that the QR code vote is different from the human readable vote. A recount, by running the paper ballots through the machine again, would come up with the same result as the first time. The only way to catch it would be to hand-count the paper ballots and compare the results to the machine counted votes. Really though, the QR code should be eliminated, so that the voter is able to personally verify what the machine will actually read.