the fix is all about telling the browser that we need from 60px (topbar + padding) to 90px (topbar + padding + editor toolbar) of space at the top when scrolling.
I have a theory in my head of how to build a regression test framework for something like this. If/when I get to lift this out of the idea phase into a practical solution, I can probably make time to build it for you.
yesterday I finally succeeded in reproducing it on Brave (osx)
the fix is all about telling the browser that we need from 60px (topbar + padding) to 90px (topbar + padding + editor toolbar) of space at the top when scrolling.