System Settings doesn't close and continuously changes focus to itself from any other window

I just upgraded to Ubuntu 16.04 from 14.04.

When I run System Settings, my CPU usage goes to 100%, and the Settings window always remains in focus. I tried to open System Monitor to kill System Settings, but the focus kept on changing back to Settings. When I click the close button, the current instance of Settings closes, but at the same time a new instance of the window pops up.

The only solution I found was to log out of the system.

Output of apt-cache policy unity-control-center:

unity-control-center:
  Installed: 15.04.0+16.04.20160413-0ubuntu3
  Candidate: 15.04.0+16.04.20160413-0ubuntu3
  Version table:
 *** 15.04.0+16.04.20160413-0ubuntu3 500
        500 http://jp.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     15.04.0+16.04.20160413-0ubuntu1 500
        500 http://jp.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

This was a bug that has since been patched. The version of unity-control-center shown in your output from apt-cache policy unity-control-center is out of date.

I issued the following commands:

sudo apt-get purge unity-control-center

sudo apt-get install unity-control-center

sudo apt-get install unity-control-center-signon

Note the change in output.

$ apt-cache policy unity-control-center
unity-control-center:
 Installed: 15.04.0+16.04.20170214-0ubuntu2
  Candidate: 15.04.0+16.04.20170214-0ubuntu2