Black square?

Question

Adobe After Effects

I just can’t figure out what’s the matter, I create an animation in ae on a green / red background, render it, throw it in sony vegas and throw the chroma key effect, select the desired color and the color is removed, but a square appears from somewhere in the middle, and there’s no way to remove it , in ae there is no bottom layer, but I tried everything but it remains, reinstalled the version, where does it come from?