Firefox 80.0.1 Linux
.attention-bar-nsi.fixed { position: fixed; width: 100%; z-index: 9999; top: 48px;}
999 works
Odd, not happening in Chrome.
If you scroll down the page does it happen? Still happens for me in Chrome also, and on Windows.
Ah sorry, I didn't see the part about you needing to scroll down. Yes, this happens to me on Chrome in Windows as well.