I'm still going to be giving this 5 stars even though there is a major issue involved and I hope you are able to patch it. I cannot watch any 18+ videos. It gives me the popup saying
"This video is age-restricted and only available on YouTube.
Learn more
Watch on YouTube" and when I click on "Watch on Youtube" it opens a new window with the same message displaying. I have tried to mess around in inspect element to fix it but nothing works. As for fullscreen it works flawlessly if you have picture in picture mode on, you just cannot use auto generated subs in fullscreen which is fine.