normal vector flipping with Circle CNR

I'm trying to make a circle that travels along the circumference of another circle.  I also used Point on Curve to place a point on the moving circle.  When I use Circle CNR, the moving circle changes orientation periodically

I've attached a file to illustrate what I'm talking about.

I used Circle CNR to make the moving circle.  The center point is a point on the stationary circle and the normal vector is a vector from the center of the stationary circle to the center of the moving circle.

The orientation of the moving circle seems to flip every pi/2 radians--at pi/4, 3pi/4, etc.  I can tell because the point on my moving circle jumps from one side of the circle to the other.  I think this has something to do with the way the Circle CNR component works.  If I start with the same vector, find two vectors normal to it, use them to define a plane, and use that plane to define the moving circle, everything works out fine.

Can anyone explain to me why this happens?  Is there a way to solve my problem that's faster than making a new plane or adding extra components to reverse the vector half of the time? (I'm new to Grasshopper.)

Thanks!  I'd appreciate any ideas.