The video is showing some of the problems that can occur when importing from Illustrator into Cinema 4D, particularly on Lathe objects. A major point is to hit Command-Y in Adobe Illustrator to switch out of preview mode and into ‘artwork mode’. This shows the actual bezier points and vectors that will be imported, which is all Cinema 4D cares about. The Preview (normal view) in Illustrator is showing you how the illustrator file will print on paper, and is not really showing accurately what is in the file. Shapes can be on top of each other, or hidden in Preview mode, which Cinema 4D really does not like.