Strange fragments on stage after tween

Hi all,

I’m currently working on a project involving a circle animating clockwise and anti-clockwise, there is a mask covering the circle and animating in over 40 frames ( 10 frames for each quater )

However when the circle tweens out, there seems to be a trail / fragments left on the stage which makes the animation look horrible and jerky

Has anyone come accross this before?

Any help is appreciated, thank you