Redraw path with pencil tool does not work as expected

At 4:40 of this video you can see that the pencil tool can perfectly redraw the path of the letterform.

When I try to do exactly the same thing I seem to get really random results where sometimes it does redraw perfectly and others where it redraws a line shown attached in the image. I am drawing from the anchor point and ending on the path, it's almost 50/50 whether it works. 

Is there a way to make this tool more reliable?  I've played around with the settings and they don't seem to make a difference and I've tried it on a seperate OS with the same results. It just does not work as smoothly as in the video.