Oh, I have no doubt that it was “calibration error.” My question is who did the calibration on that machine, as well as any others used by Republican voters in that precinct. In my experience, Republican-registered voters are often pointed to different voting booths than are Dems (not sure about other parties or Independents; maybe they get their choice), so it would be simple enough for someone to calibrate the touch screens of those intended for GOP voters so that the selection registers a vote for the Dem candidate.
And that implies that the touch sensitive map had to be tied by code to the democrat choice. Coding a cheat is not the same as calibrating a touch sensitive map area to appear in a specific position.
Taking either point of view, it is blatant cheating, something the democrat party has done for many decades.