It looks like Vimeo changed how their embedding code works at some point; and our embed code could use a little cleaning...
Change the Resulting Markup on the Vimeo tag to:
<div class="video-container"><iframe frameborder="0" width="500" height="300" src="https://player.vimeo.com/video/\\2" allowfullscreen></iframe></div>
And now its mobile too

... The regex could probably use some love to account for the staffpicks url, but this should work fine.
Vimeo URLs:
https://vimeo.com/1654340
https://vimeo.com/channels/staffpicks/315528770
It doesn't help that their site isn't the easiest to navigate, or every time I try to sign up for an account it stresses that it can't continue because for some reason I'm identified as a malicious user even though I don't even use their product...