On Demand playback not smooth 

A YouView Box FAQ

Programme and film content can be created in different ways, and from different parts of the world. Changes in content based on region and the creative choices of the director can mean content is displayed at different frame rates.

When playing video content back from the player through the YouView box, it will adapt the content to ensure playback is seamless, but this may differ from how it was originally created. The adjustments to playback may sometimes not appear smooth, or appear as a judder on screen, this may be particularly noticeable on Ultra HD content or on fast moving scenes.

If the motion judder reduces the quality of your experience, you can try adjusting your TV settings to improve programme playback. Some TVs may have advanced picture processing settings which can be changes or turned off to improve the picture e.g. Motionflow on Sony TVs.