Math for returning to higher offset items appears off

[isolationism]

Your own demo does this as well, though less reliably than my own work with more items and a larger offset. Observe this recording:

You can see the issue happens twice; once when I click "Section 2" then again when I click "Section 1". Also note as I click "Section 3" afterward, it momentarily jumps to highlight "Section 1" before sliding down through the other items.

It appears as though the window needs to scroll up an additional pixel or three to trigger activation of the correct menu item. It only occurs when scrolling up; I have never seen the issue when clicking an item that scrolls down.

[pettiboy]

Hi @isolationism!
Thank you for bringing this to my notice.
I have fixed this issue on Demo2 by adding an offsetBottom.

For your own work you can try the following:

• Reduce the value of scrollThrottle.
• If your page contains a navbar a header don't forget to add the following CSS

html {
  scroll-padding-top: 120px;
}

• Try using offsets.

Let me know if this solved your problem!