The volume control for the youtube handler in version 2.6 appears to have broken at some point (and browsing the repository it appears to still be broken). It seems the element name that the youtube popup window uses has changed from 'video-player' to 'video-player-flash'. Replacing the instances of 'video-player' in the popup youtube section with 'video-player-flash' seems to have fixed it.
The volume control for the youtube handler in version 2.6 appears to have broken at some point (and browsing the repository it appears to still be broken). It seems the element name that the youtube popup window uses has changed from 'video-player' to 'video-player-flash'. Replacing the instances of 'video-player' in the popup youtube section with 'video-player-flash' seems to have fixed it.