I'm using Chrome for Android and the YouTube app on a note 4. It seems to happen with about one in three video links.
Happens to me as well on Chrome/Android. When it happens, click and hold the link to the video and copy the link address. Paste it into your browser and you'll see there are multiple "watch?v=" in the link. Delete one of of those and it works. Not sure why that happens, may be a bug on the DGCR end to report to Tim?