Used the Rotoscope brush to remove the background of video, but leave person. When exported in Media Encoder the person is randomly disappearing into the background.

I rendered frame by frame with the roto brush to remove a person from their background. I imported a new background from a photoshop file. I exported the file with media encoder and the mp4 it create has parts of the person randomly disappearing into the background. I go back to the After Effects file and none of these errors are visible. I've used this tool for 7 other videos in the last week and haven't had this issue. Please Help!! On a deadline!