Let's say I've got 100 episodes of NOVA. I've added one episode to a playlist about a certain subject, and there's a bunch of other videos in that playlist about that subject.

I go into the playlist and click the play button. This is the play button on the playlist, not the individual video in the list.

My expectation is that the next video it plays is the next video in the playlist. However, repeatedly, it plays the next NOVA video instead of the next video in the playlist.

What am I doing wrong here?

Clarifying: it finishes the first video in the playlist, but then continues on to a video that is not in the playlist.