I used Mocha to motion track a phone and created new text to put on it. That was all in a separate comp. I then took that comp and placed it over the original footage and used Match Grain to match the grain (duh) of the original footage to the new text. However, it created a white box outline on the video, as seen here:
It took me a while to figure out it was Match Grain causing the box. How can this be eliminated?