Hello again,
I was wrong. It is not when the cursor is on the lower pane but at the bottom of the webpage. I just found that out, wanted to edit my original story but accidentally hit the waste paper basket icon.
I found that out when I moved the webbrowser window to my other monitor to see if it happens there as well. Since that monitor has a larger resolution, the window was smaller and so I saw that scrolling starts when the cursor is at the bottom of the web page, still a long way from the panel.
I use the Brave browser and when copying the web address of a long page into Firefox it does not happen. In other words I guess it is something in Brave.
I will look there to see if I can find something. Should you know what it is then please let me know.
Thanks again.