I am trying to produce a video with a freeze frame of a person kneeling down and I am trying to have that person walk up from behind and "capture" himself and walk away. But no matter what I try to do the top video track keeps taking precedence over the lower track. Plus, I wind up with a lot of yellow dots but no person inside. I never had this problem before, but now I can't seem to get it to work at all. What am I doing wrong??