When I click on a video in YouTube (in Standard View), at the same time as the dialog box pops up, the video starts playing in the background, as if I selected "Show the webpage". So if I choose "Play the file inside the player" it plays on top of each other, so to avoid double audio, I have to exit Display View to stop it on the webpage, and then go into Display View again.
It's been like this for a couple of years, but it didn't do that before. Very annoying, since I mostly use Standard View to watch YouTube videos.
And I've tried all browser engines and all sorts of settings, including updating Chrome, Explorer and Firefox on the computer, but nothing helps.
Also having the problems you describe, and it's not video specific, which means one video can play okay one day, and the SAME video can't play on a different day. Sometimes I restart MC, and it suddenly plays, other times it doesn't. And some videos won't play at all...