Thanks guys, I understand how complex it must be to run the math on these kind of operations. Hats off to Michael in that regard!
I thought I was keeping things relatively simple in this case as I used the same shape twice and produced the copy via a precise rotation using the center of the circle as the pivot point. In theory the 2 shapes should still be in precise alignment. They certainly look to be aligned when I zoom in like advised. I can only think the sweep operation has produced an object with small surface irregularities that become apparent when you rotate the shapes around the axis.

I attach the model file Michael.

Thanks for the help!

Dave