The problem was that he was pressing the Origin button after placing the tip of the blade inside the mark.

If that button is pressed then the plotter will perform the AutoScan Mark feature which is when the head sweeps in 45 degree angles in search of the first mark, if the plotter starts doing this after the end user has placed the tip of the blade inside the mark then the sensor/head will sweep away from the mark eventually giving the end user a Scan Mark Error.