**Steps to replicate the issue** (include links if applicable):
* Log into Vector
* Visit https://en.wikipedia.org/wiki/Initial_campaign_of_the_Breton_Civil_War on a large screen with the table of contents in the left sidebar by default (refresh page after correcting if not present)
* Scroll down to show the sticky header
* Move the TOC to the sticky header by pressing the "hide" button in the TOC
* Note: the incorrect spacing: {F71597931}
* Decrease the viewport so that the sticky header disappears
* Increase the viewport so the sticky header is back
* Click the TOC button to see the TOC doesnt work
**What happens?**:
{F71573221}
{F71573238}
**What should have happened instead?**:
The TOC should still work after changing viewports
**Software version** (on `Special:Version` page; skip for WMF-hosted wikis like Wikipedia):
In production on english wiki
**Other information** (browser name/version, screenshots, etc.):