We are aware of the issue, and are working on a solution.
https://support.google.com/youtube/answer/6098135?hl=en
"As we upgrade the YouTube Data API to bring more features, we’ll begin shutting down the old version on April 20, 2015.
If the video appears unexpectedly in a web browser, it means that website is using an outdated method to access YouTube videos."
Videos already imported, seem to be unaffected at this stage. It's the import process which they have changed from the looks of things.
Matriarch
