I am seeing the same thing. But the issue seems to be confined to only those that appear at the very top of the page. If I select one from one of the categories like News or Sports, those all play as they should. Are you seeing the same thing? I have the same version of Safari you do.
Since I posted above, I've updated my iMac to High Sierra. During the process, I also updated my Flash player for Safari through Xfinity. Now the videos all play as they should. Right now the top area is for live TV programs instead of videos.