... #Firefox showed this in the glitched version when reopened in a new tab; setting the "hardware acceleration" did not have any effect ...

https://www.youtube.com/watch?v=Fyi13rej0Vc

... so were the two previously mentioned videos. :-/

In #MSWindows11, via
"Settings: System: Display: Graphics: Custom settings for applications: Add an app: Add desktop app", added "firefox.exe" path; then set "GPU preference" to "High Performance ...".

Firefox being put in "Efficiency mode" brings back the glitchy playback.

... To #MSWindows11 [Copilot] key do nothing at all via #AutoHotkey, in "neuter-copilot.ahk" file ...

#Requires AutoHotkey v2.0

InstallKeybdHook

; Does not disable [Copilot] key.
;#C::Return

; Scancode does not work.
;SC0x000100003100::Return

; Works: Does nothing.
#<+F23::Return

; Send [Ctrl]? Does not work: "Ctrl+R" does not reload the Firefox tab.
;#<+F23::^

... Also, after installing #Firefox ESR v128 (from firefox installer) in a different location than previously installed v133, binary from v133 stopped working.

I was thinking to have multiple versions installed to easily test. But that was not to be😞

#MSWindows11

... Seemed for #Firefox v133 https://www.youtube.com/watch?v=DKJciQaCbX8 video played without issues, but not https://www.youtube.com/watch?v=oVjcPAdU028 .

Tried all 3 ways -- (non)MSIX package via "winget" & via Firefox's own installer -- to install ESR 128.5 version, without improvement.

On seemingly unrelated issue of delayed playing, found https://www.elevenforum.com/t/youtube-issue-or-browser.31662/#post-540480 to …
- not "Use recommended performance settings"
- but "Use hardware acceleration when available" instead

… seemed to have resolved for the ESR version.

#MSWindows11