Hello, I have the exact same problem with the vimeo.com site, clicks are not registered after the video started playing. I think it may have something to do with the wonderful Opera option to play the video outside the browser, since it started to happen with an update when the button icon changed from black to green, hope this helps a little bit. Please fix my vimeo I use it everyday and I love to use Opera with it.
thanks in advance opera team!
(MacOS Sierra 10.12.2 , Opera v46.0.2597.57)