You are the first to report an issue like this. Let's see if we can solve this. If you would answer some questions:
- Are the videos laggy from the start, or after the game has been open for some time?
- Is there any difference in video playback with "full screen" and smaller game window?
- Are you playing on PC or laptop? What operating system?
- What model is your graphics card? Do you have the latest drivers installed?