For a long time, and with good cause, people have been complaining there's no way to contact YouTube about issues with video playback.
It's a bit too early to say just how well this one will work, but in recent weeks they did add several items, from diagnostic tools to a link for reporting playback issue to the 'face' of videos themselves. I know I'm hoping these will work, or at least work a bit better than what has been in place so far.
Gradually, Google is coming to realize that they are not operating in a vacuum, so hopefully this is just one sign of additional options to come? Don't expect miracles, though.