OS 11 react the Section Index fixed no longer works as it did in the web app

I used the Section Index a lot in OS10 and later OS11 web app, but now using it on a react web app and the "fixed" attribute no longer works, it is NEVER fixed, it scrolls off the screen when you scroll, it used to work in standard web apps, I now have to manually code this GRRRRR.

Hi Elize,

i don't know how it worked in O10, haven't been around long enough, but I had a quick try and it seems fine to me.

See attached oml.  I does scroll to the top of the screen, but then stays there and doesn't disappear off the screen.  Can you show a demo of how it is behaving for you ?