Hi ctabedzki, Reading your post, my first suspicion is an extension or extensions. Redundant extensions sometimes don't work well together and can cause unexpected results. You can try disabling one or two like Ghostery, uBlock Origin or Disconnect to see if the problems persists.

Or, you can try Firefox in it's Safe Mode which temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes) that might be causing problems.

With Firefox open: Select Menu Select Help Select Restart With Add-ons Disabled On the dialog select Restart On the next dialog select Start In Safe Mode (Do Not select Refresh)

With Firefox closed: Press and hold the Shift (in Mac: Option) key Launch Firefox On the dialog select Start In Safe Mode (Do Not select Refresh)

(Your Bookmarks Toolbar will be turned off. Right-click on the Toolbar and select Bookmarks Toolbar to display it again.) ______________________________________________________

To quit Safe Mode: Select Menu Select Help Select Restart With Add-ons Enabled

Or Exit Firefox. ______________________________________________________

(BTW - Lightbeam is no longer supported)

Maybe remove not active (disabled) extensions or create a new profile to remove all remnants from Firefox versions.

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile