Show Desktop keyboard shortcut stops working after taking screenshot

[Teo]

These steps systematically reproduce the issue:
1. make sure you have some application window on the foreground (e.g. Google Chrome)
2. hit Shift+PrintScreen to take a partial screenshot
3. Select the area for the screenshot by clicking and dragging
4. (IMPORTANT) Use the dropdown selector to choose a location other than the default for choosing the folder to save the screenshot to (if you skip this step you won't reproduce the issue)
5. hit Ok
=> the screenshot is saved and the Screenshot application is closed
6. Hit Ctrl+Super+D (repeat several times if you like)

Expedted behavior: after step 5 focus should be returned to the application that had it before you took the screenshot. And most importantly, whether or not this happens, step 6 should show desktop

Observed behavior: after step 5 the application on the foreground has lost focus, and at step 6 Ctrl+Super+D does nothing

Note that even if it's the Screenshot application triggering the issue, either Xorg or Unity, or whatever piece of software is responsible for keyboard shortcuts and for showing the Desktop, MUST guarantee that (i) keyboard shortcuts always work and (ii) show desktop always work. So, no matter whether or not the Screenshot application is doing something wrong, the mere fact that a buggy (or malicious) application can prevent Show Desktop from working as expected represents a bug in the piece of software responsible of keyboard shortcuts or of the Show Desktop action (whichever of them is failing).

The Screenshot application probably has a bug in that it fails to return focus to the application which had it, but again, this should not prevent the Show Desktop shortcut from working.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: unity 7.3.2+15.10.20151016-0ubuntu1
ProcVersionSignature: Ubuntu 4.2.0-25.30-generic 4.2.6
Uname: Linux 4.2.0-25-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CurrentDesktop: Unity
Date: Sat Jan 30 17:19:40 2016
InstallationDate: Installed on 2013-10-11 (840 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
SourcePackage: unity
UpgradeStatus: Upgraded to wily on 2016-01-18 (12 days ago)