Note that you can control this pref via the right-click context menu on the Downloads button, so no need the use about:config. Note that the name of the pref is ''browser.download.alwaysOpenPanel'' and its Boolean value should be false to make this work. This setting is about opening the panel when download starts. The toolbar button should animate during the download and get an accented color when all downloads are finished and shouldn't open like you wrote. Start Firefox in <b>Troubleshoot Mode</b> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if <b>hardware acceleration</b> or if <b>userChrome.css/userContent.css</b> 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