Hi, I do not use this plugin on my site in order to achieve fluid video widths with proper aspect ratios, but I just had the same problem you did.
Do you have JetPack installed for your site? Mine does, and the recent JetPack update was the culprit. I had to turn off the ‘Shortcode Embeds’ feature in the JetPack settings. Now everything is back to normal.
I hope this proves to be true for you as well.
