More recently playlists have been looping the same song at seemingly random, looking to support forumss gives hundreds of comments reporting similar behaviour. (https://support.google.com/youtube/thread/16267152?hl=en)
Is youtube trying to drive adoption of youtube red by intentionally reducing the user experience for non premium users?
[0] https://www.w3.org/TR/page-visibility-2/
[1] http://daniemon.com/tech/webapps/page-visibility/
[2] https://testdrive-archive.azurewebsites.net/Performance/Page...
The looping is quite different though, there's no legitimate use for it, and I can't find any controls that would allow you to set a song to auto-repeat. So it's either a bug that they're struggling to fix or an intentional change to make play-lists less functional when you are not watching the platform.
I do get that "video paused" popup every once in a while, but I have never seen the looping behavior.
If this is happening to you a lot, a cool way to get around it can be using mpv/youtube-dl, they both support YouTube playlists:
mpv --no-video https://www.youtube.com/playlist?list=PLThlnilAqSEtI9HNfZEEy...
or
mpv https://www.youtube.com/playlist?list=PLThlnilAqSEtI9HNfZEEy...
The --no-video flag hides the mpv OSC (a simple GUI, which is not necessary if you're playing songs). To navigate the playlist you'll need to learn a few keyboard shortcuts (<, >, ENTER, p), and more:
https://mpv.io/manual/stable/#keyboard-control
This works very well and is multi-platform.
Unless YouTube puts DRM on the whole site, this should continue working as long as you keep mpv or youtube-dl updated. Sadly I don't think we can know for sure if they're doing this on purpose.