I'm having the same issue. Turns out that the **Proxy render size** under **View Settings**, Really destroys the accuracy of the video in preview.

Notice how the 'Text' and 'Character' deviates from its original location.

[![Notice how the Text and Character deviates from its original location.][1]][1]


  [1]: https://i.sstatic.net/glThM.jpg


The solution I found for myself is to fix all the glitches in **full render** settings.