One other possibility is that the camera was positioned in the correct place, but was angled slightly to the left with respect to the line, rather than being ex

One other possibility is that the camera was positioned in the correct place, but was angled slightly to the left with respect to the line, rather than being exactly parallel with the line. I don't know how they set up these cameras to ensure they're parallel with the line, but this seems at least as likely as aligning the camera parallel but in the wrong place. I'm not sure how you'd be able to tell from the images though, but it would make a much bigger difference to the actual result.