December 26, 2014 at 12:31 pm #22027
On the file, those “moving a bit” parts do conspire to form a circle there. You can see a bit of the same thing on the thingiverse page. ( http://www.thingiverse.com/thing:84044 )
One thing that could be contributing to the difference is just how “wet” the tip of the pen is. It’s drawn quite a bit more ink on one side than the other, and could be leaving a different amount of ink behind for that reason.