Docky: top bar shadow blinks during scroll on icons in dock

When i just move mouse orver icon in dock - everything is fine, no any blinking.
But when i move over some application icon (which is running and have several windows) - when i do scroll between windows, ie switch between windows by scrolling, top bar shadow switches from gradient to black line and viceversa.

Ubuntu 14.04 LTS
Details of a package:
$> dpkg -s docky
Package: docky
Status: install ok installed
Priority: optional
Section: x11
Installed-Size: 3350
Maintainer: Ubuntu Developers <email address hidden>
Architecture: all
Version: 2.2.1~bzr1845-0ubuntu1~13.10~dockycore3
Replaces: python-docky (<< 2.0.99)
Depends: mono-runtime (>= 2.10.1), libc6 (>= 2.17) | libc6.1 (>= 2.17) | libc0.1 (>= 2.17), libdbus-glib2.0-cil (>= 0.6), libdbus2.0-cil (>= 0.8), libgconf2.0-cil (>= 2.24.0), libgdk-pixbuf2.0-0 (>= 2.28.1), libgkeyfile1.0-cil, libglib2.0-0 (>= 2.38.1), libglib2.0-cil (>= 2.12.10-1ubuntu1), libgnome-keyring1.0-cil (>= 1.0.0), libgtk2.0-0 (>= 2.24.0), libgtk2.0-cil (>= 2.12.10-1ubuntu1), libmono-addins0.2-cil (>= 0.6), libmono-cairo4.0-cil (>= 2.10.1), libmono-corlib4.0-cil (>= 2.10.1), libmono-posix4.0-cil (>= 2.10.1), libmono-sharpzip4.84-cil (>= 1.0), libmono-system-core4.0-cil (>= 2.10.3), libmono-system-web4.0-cil (>= 2.10.3), libmono-system-xml-linq4.0-cil (>= 1.0), libmono-system-xml4.0-cil (>= 1.0), libmono-system4.0-cil (>= 2.10.7), libnotify0.4-cil (>= 0.4.0~r2998), libwnck2.20-cil (>= 2.26.0), libx11-6 (>= 2:1.6.0), librsvg2-common
Recommends: dockmanager
Conflicts: python-docky (<< 2.0.99)
Description: Elegant, powerful, clean dock
 A full fledged dock application that makes opening common applications and
 managing windows easier and quicker. Docky is fully integrated into the GNOME
 Desktop and features a no non-sense approach to configuration and usage.
 It just works.
 .
 Docky provides an application launcher, running application management, and
 various "docklets" including a CPU monitor, weather report and clock. It is
 similar to other docks such as AWN and cairo-dock.
 .
 Applications can integrate with Docky to add extra items to their context
 menus or modify their icons to display more information. This package
 includes integration helpers for a number of applications, including Banshee,
 Rhythmbox, Deluge, Tomboy and Zeitgeist.
 .
 Docky is derived from the GNOME Do "docky" interface.
Homepage: https://launchpad.net/docky
Original-Maintainer: Debian CLI Applications Team <email address hidden>