We have just recently started using the plugin and have seen a similar issue. It looks like it’s specific ad creatives that are busting out of the iframe as they are called into a smaller slot size. Call is for a 320x50 but then a 300x250 is rendering.
We threw in a CSS override to prevent the ad from blowing out for now till we can figure it out.
It’s on a limited set of creatives, looked like maybe Adsense coming through GAM.