Last week a number of people ahead of us on line for a single kiosk could not figure out how to stand and look at the kiosk so that it would take their picture and recognize them, which resulted in them being moved to another line. This slowed down the line, as they stood there for longer than usual until the CBP agent told them to stand aside. We had no problems and were quickly recognized. This was at EWR, but I don't believe that mattered.