Need to clean up a mask in Mocha

I have a mask in Mocha around a photo I want to lay over a clip. When the clip renders, the mask slips - and the mesh goes pretty wide outside of the initial frame. Every time I try and go frame by frame to try and add points to clean up the mask, the mask disappears

Try re-tracking, it sounds like a corrupt track. Do not use perspective when you track, as that might be causing the issue.