Can we see this miracle?!

Are you running Firefox maximized? Does it work if you make the Firefox window smaller and position the title bar lower?

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

When I invoke Print Screen the context menu disappears so a screenshot is not possible. Yes, I am running FF maximized, and when I resized and moved the screen about the context menu would travel with it. It is not always the 7th or 3rd or 1st item in the bookmark list, what seems to be important is the relative distance of the bookmark to the title bar. I have just now discovered that this happens without accessing bookmarks in FF, it happens in other programs, too, the issue seems to be invoking the context menu and the distance of the selected item from the title bar. Troubleshoot mode in FF did not alter the behavior, and it has been decades since I have had to think of things like CSS and Acceleration so I no longed know how to check those things. We want our machines to run perfectly, would that the world were so, but this problem is only an annoyance so I will not lose sleep over it, I'll just find a way around it. Thanks for taking the time to think about this. If I can be of any further assistance please let me know and I'll try to help out.

When I just discovered that the problem is based on the context menu I should be clear. The problem occurs when the top line of the context menu (Open in New Tab) overlaps the title bar area, thereby rendering the top line unavailable for execution.