It is best to restart Firefox in safe mode. To do this, access the Help menu and select the Restart with Add-ons Disabled option.

Thanks for the reply. I made a mistake, it is YouTube where I have the video problem, not Facebook. Nonetheless, I will try viewing the YouTube video in safemode and see if that makes a difference. I will get back to you when I do. Thanks.

Made the change using FF in safemode while viewing YouTube video's. I now for the most part DON'T have the same problem with video freezing and slowness. What does that tell you? Is there something going on with my options issue or add-ons? The only add-on I have is uBlock. Could that be the issue? If so, is there a add blocker that causes no video issues? Can you help? Thank you.

You can try to disable hardware acceleration in Firefox.

• Options/Preferences -> General: Performance
  remove checkmark: [ ] "Use recommended performance settings"
  remove checkmark: [ ] "Use hardware acceleration when available"
• https://support.mozilla.org/en-US/kb/performance-settings

Close and restart Firefox after modifying the setting for changes to take effect.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration