How is that shield made? Is it a 3D element rendered in another package? A shield in element 3d or Zaxwerks? Or is it just an image that’s had its 3D button turned on in AE?
I looks like the shield as a photoshop file or a png that doesn’t have an alpha (if its a jpg then there’s your problem; jpgs can’t have alphas) and you are seeing the boundary of the image. Check the interpretation settings in the project window for that element – it could be AE couildn’t figure out what do alpha wise and you can force AE to assume a straight or premult alpha