Did you try to close (Quit) and reopen Firefox ?

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 userChrome.css is causing the problem.

• switch to the DEFAULT 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

Hi,

  Thanks for your reply. Yes, this is not just a restart issue, this has persisted through computer restarts, but it only began a few weeks ago. But I never restarted when blockreload was true. Could that be the culprit? If I use Safari, I do not get this problem. I did go into Troubleshooting mode. There are two add-ons, Firefox container and  ... Duckduckgo. And hardware acceleration is turned off. 

 Thanks for any additional suggestions you might offer!