Surrounding Movieclips "shakes" and "vibrates"

I often have this problem but didn’t really care about it when it doesn’t appear to be too apparent. But this time, it is quite obvious.

There seems to always have a problem in some of my animations when I have movements involved for clicking something. Say for example, I have a button that will slide a banner downwards when clicked, the layers or MovieClips beneath and around the sliding banner seems to “shake” and “vibrate” while the banner slides. The shaking and vibration stops when the animation stops.

Now, I didn’t have this problem when I publish the SWF in Flash(though I have this problem sometimes in the SWF) but when I load it in Flex, the movieclips around the moving movieclip in the SWF file shakes. It looks as if the layers of movieclips are “rubbing” against the moving movieclip.

Why is it this way? And how could I fix this?