I've noticed that problem too. However, that problem isn't due to Festool doing anything wrong. I think its great that they put the videos on YouTube. YouTube is a major marketing channel now. It is like the library for things that were on TV or the movies. It is on demand reference and advertising. In this day and age it would be stupid for them to not be on YouTube.
As an example, a few hours ago there was a video for a RAS sander. I had never considered buying one, and others probably didn't either. But to see it demo'ed like that, who knows how many they sold off that short video. I sure want one now.
The reason it is starting and stopping has to do with bandwith problems. Lots of people using the internet where you live while you are trying to use it, or you have a slow connection.