When the YouTube video has chapters (e.g. https://www.youtube.com/watch?v=WB7OfwTvJ6c), the aspect ration button does not appear. In fact, the entire ytp-center-controls class does not appear, and Chrome's inspector shows it is below the frame.

I had to add in a workaround that just prepends 'ytp-arc-listandytp-arc-buttonto theytp-right-controls` class. Doing this seems to work whether the video has chapters or not.