As the title says, a couple of days ago I noticed that all progress bars in YouTube thumbnails have disappeared. The "Watched" text is also gone. I tried clean reinstall, removing all add-ons, but it did not help. Just to check, I installed Chrome - everything visible (see image - FF left, Chrome right), which would suggest that something is up with Firefox. I also check the history settings on YouTube, everything is turned on, and I see viewing progress in thumbnails when I'm on the history settings page, but not on "normal" YouTube.

I would appreciate any sort of help or advice. My life doe snot depend on this feature, but I really like it and it helps navigate YouTube more efficiently.