Photoshop :: Circles Changing When Rotated

I'm trying to create a white ring that will move on top of a grey ring (for a video). However, even though I used the fixed aspect ratio, & copied the grey ring to make the white ring, with both in the same position; whenever I rotate the top (white) ring, it doesn't line up with the grey ring underneath at certain points, it seems to be not a perfect circle. So when I add the two images into a video editor & rotate the white ring, it doesn't line up with the grey ring below.