I have tracked down the bug and submitted the patch to gnome-bugs #171938. This is my first patch ever and I'm rather curious how things go on from here :)
-- auto-hidden panel sometime jumps to the top of the screen https://launchpad.net/bugs/48226 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
