Why is my impeller moving up and down on a simple rotation?

[nomiec40838729]

I need the impeller in the logo to stay in the same position when spinning.  Why is it moving up and down?  In my timeline, the anchor point, position and scale values stay the same from start to finish but visibly, it's moving up and down. 

[Rick Gerard]

The Anchor Point is not in the center of the graphic.