Greasy Fork

Breaks the following script outside of subscriptions: https://greasyfork.org/en/scripts/13040-youtube-hide-watched-videos

Waterfox Classic, ViolentMonkey

What are the settings for YPEF? And how exactly does script breaks?

Also, be aware of https://greasyfork.org/en/scripts/13040-youtube-hide-watched-videos/discussions/157057 (was posted after last update of the script).

"Hide Guide" and "Remove size limit for video titles" are the only options enabled in YPEF.
When YPEF's enabled, the "hidden" state stops working for all other pages than Subscriptions.

Is option "Set thumbnails width" in "Front page" group set to anything other then "default"?

If it is then should be fixed with 2.21.1.

Yes, working fine now.