Did something break/change with video preview thumbnails recently?

I have 4 or 5 libraries where preview thumbnails are enabled. The behavior used to be that scanning in new media would add titles, detect intros, detect credits, generate chapter thumbnails, and generate playback thumbnails.

Now, adding titles only detects intros & credits. Chapter and playback thumbnails only generate if I analyze the new title. And even that's kind of broken. Like, if I add a whole season of TV shows, analyzing the whole season doesn't work. I have to analyze each individual episode, one-by-one, to generate thumbnails.

Looking at Library settings, I have "Generate video preview thumbnails" and "Generate chapter thumbnails" set as "as a scheduled task and when new media is added". I haven't changed any general library settings in... I don't even remember when. Probably a couple of years.

Is there another setting I need to change or update to restore old behavior where it generates thumbnails whenever I add new titles?