Well, last week Firefox was grinding slow so I resurrected Ghostery Dawn which I'd previously tested but not used in earnest. GD is faster and I got all the same FF plugins installed and copied my saved logins and bookmarks. One snag, whilst it responds correctly to clicking on links in webpages it won't open links in other apps, eg email or Twitter. Even if GD is already open clicking a link (from another app) opens a new instance at the home page.

So I did a 'Remove Completely' of FF in Synaptic, ran updates and re-installed. And lo, it works much better. But after a time it goes slow again.

Running it from a terminal I get this:

*phil@phils*:*~*$ firefox [GFX1-]: glxtest: libEGL missing methods for GL test [GFX1-]: glxtest: libEGL missing eglGetDisplayDriverName

Checked libEGL is installed and it is. So moving on, opened a YouTube video and get this in the terminal:

2022-04-24T12:56:32Z*ERROR* mp4parse] Found 2 nul bytes in "\u{0}\u{0}" [2022-04-24T12:56:32Z*ERROR* mp4parse] Found 2 nul bytes in "\u{0}\u{0}" [2022-04-24T12:56:32Z*ERROR* mp4parse] Found 2 nul bytes in "\u{0}\u{0}" [2022-04-24T12:56:33Z*ERROR* mp4parse] Found 2 nul bytes in "\u{0}\u{0}"

Despite the error the video plays OK. Every time I choose a different video I get the same four lines though with different (time/ID?) numbers before 'ERROR'.

Does anyone understand this? And is it likely to have anything to do with the performance issues?