After Effects glitches in playback and render

I have footage glicthes in my edit and its not going away. Everytime i purge all memory and cache its something new and when i render the edit it has different glitches?? the frames are mimicking frames that i already have and its making me angry cos i worked hard on this and i cant seem to fix it. even rendering with media encoder the glitches appear. what do i do???