youtube has recently been implementing download speed throttling on some video downloads. See: https://github.com/ytdl-org/youtube-dl/issues/29326 . Youtube-dl does not yet have a solution for this occasional download speed throttling.

This yt-dlp fork has a workaround (though not a true fix) for the issue: https://github.com/ytdl-org/youtube-dl/issues/29326#issuecom...