Hi, if the reinstall works for the Desktop as I believe I saw that then you will have to do that again to fix the issue. The problem lays on the other systems you are Syncing to which you did not mention what they are. So that is where the problem is coming from, 1 of the settings where it is syncing is corrupted or been changed so sync changes you. Fix the other system with reset or something if a mobile or ask over here : https://support.mozilla.org/en-US/ If it is another desktop then try the reinstall if it is experiencing the issue. you can also test hardware acceleration and extension and a few other things by checking in : SAFE MODE *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes In Firefox Safe mode these changes are effective: *all extensions are disabled (about:addons) *default theme is used (no persona) *userChrome.css and userContent.css are ignored (chrome folder) *default toolbar layout is used (file: localstore-safe.rdf) *Javascript JIT compilers are disabled (prefs: javascript.options.*jit) *hardware acceleration is disabled (Options > Advanced > General) *plugins are not affected *preferences are not affected TEST'''''''''is issue still there ? If yes Reinstall this way : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Reinstall with Current Release Firefox 61.0.1 with a Full Version Installer *https://www.mozilla.org/firefox/all/ Please let us know if this solved your issue or if need further assistance. So maybe it is also the data being stored on Sync and you need to clear that and start fresh. *https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips You can open about:sync-log via the location bar to see if there are recent error logs available.