Live table of contents panel on right seems broken

[meldefon]

I just spent a couple hours noticing this issue and then trying to reduce it to a minimal example. There seems to be a strange bug with the live updating table of contents on the right. Getting it to happen involves some interaction of sections/subsections and section length. I'm really desperate for some insight:

Setup

• created a fresh conda environment
• installed jupyter-book from conda forge
• used jupyter-book to create the default template book

The bug
As I scroll through my page, the current section gets highlighted in blue on the right. Once I reach the problem subsubsection (which is very long), the highlighting stops and the contents on the right becomes frozen. It only unfreezes when I reach the next subsubsection.

The length of the subsubsection is a critical parameter here, since when I shorten it to a paragraph or two the problem seems to disappear.

I've attached a markdown file here that illustrates the problem.
broken_toc.md