Pages Panel Scroll Bar Weirdness

Here is a screen-grab of the pages panel of a ~500-page doc. See how the scroller handle is at the very top of the track? Why is this the case, given that page 228 is near the middle of the document? It's annoying because I find that when I'm trying to navigate to a given page the panel, like, resets and shows the top of the doc in the pages panel, instead of whatever part in the middle where I'm currently working.