Why is the image on Youtube via Chromecast 1 slower than the sound?

When I use Youtube over Chromecast, the picture runs slower than the sound. This keeps the sound going on and on until the picture has caught up.

The problem I have only with Youtube. Netflix, maxdome or Öffi libraries are running smoothly. Electricity and factory reset did not help.

The Chromecast 1 processor is probably too weak to play the image from YouTube