Millisecond Forums

Hi,
I am working on a script where participants must place a "shield" (green arc) along the edge of a "wall" (gray circle). I've basically accomplished this using this example: https://www.millisecond.com/forums/Topic30212.aspx
 However, I'm running into a problem where as the image rotates, it is warping and not maintaining the circular dimensions of the wall necessary. I've attached my working script for reference: would there be a fixable reason this is occurring?