Kupfer frequently non-responsive to keystrokes

[Cefn]

I frequently encounter a situation in which the Kupfer window seems to be successfully focused on my Key command (CTRL+Esc), but no keystrokes seem to be sent to it when it focuses.

When first launched Kupfer is functional but on some later launch, no keystrokes will have any effect at all for selecting commands until Kupfer is Quit and reloaded ,when it becomes functional again.

I am running LXDE (as configured by Lubuntu) with Compiz as my window manager, and gtk-window-decorator.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: kupfer 0+v208-5
ProcVersionSignature: Ubuntu 3.16.0-29.39-generic 3.16.7-ckt2
Uname: Linux 3.16.0-29-generic i686
ApportVersion: 2.14.7-0ubuntu8
Architecture: i386
Date: Mon Feb 2 10:49:19 2015
InstallationDate: Installed on 2015-01-01 (31 days ago)
InstallationMedia: Lubuntu 14.10 "Utopic Unicorn" - Release i386 (20141022.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: kupfer
UpgradeStatus: No upgrade log present (probably fresh install)

[Cefn (6-launchpad-net-cefn-com)]

I've discovered that on at least some occasions, when the window is completely non-responsive (but still movable by ALT+Drag, so definitely on top in the window order) if I wait long enough, it becomes responsive again, as if there's some godawful loop running or resource request which eventually times out.