When the full category description is showing, I also encounter this on Theme Creator and on my dev instance. I’m looking into it. I suspect it’s because the route changes but the tracked variable does not.
UPDATE: I have added an expand/collapse functionality for category descriptions here. @nathank Also fixed the bug in:
https://github.com/naidihr/discourse-category-headers/pull/22
With a little nudge from Ask Discourse for using willDestroy with the router service.