The page uses a <header> with position:sticky, <main> and <footer> with position:relative.
I tested removing position:sticky from the header and changing position:relative to position:static on both and via the browser’s developer tools. However, the issue still persists, so it does not seem to be directly caused by these positioning rules.
This behavior is consistent with the issue observed on the following page: Terms Of Service ( DUPLICATE: "Smooth scroll (CSS)" setting enabled causing inconsistent scrolling with Tabs (nestable) and Table of contents elements )
While investigating, I came across a potentially related issue in the tocbot ( Tocbot ) documentation:
// CAUTION: Doesn’t work well of you already have scroll-behavior set to smooth globally in your CSS - see Flash when scrolling / doesn't scroll to right spot · Issue #273 · tscanlin/tocbot · GitHub
scrollSmooth: true,