[Bug 43060] Re: With Human icon theme mixer icon doesn't scale properly when gnome-panel is vertical.

[Marcin Antczak]

Also this mixer icon has strange behaviour when trying to set panel height to some big value.

Try to set gnome-panel height to 48 and then to 49...  and also try to set gnome-panel height to 80 and then to 81... 
On 80 mixer icon will be too small. And then on 81 will 'jump' and will be too big to fit panel, the same with 48 and 49 px.

-- 
With Human icon theme mixer icon doesn't scale properly when gnome-panel is vertical.
https://launchpad.net/bugs/43060