Consider the following scenario:
You have a computer that is running Windows 8.1, Windows RT 8.1, or Windows Server 2012 R2.
You install a Japanese third-party Input Method Editor (IME) that can toggle Caps Lock by double-tapping the Shift key on the computer.
You right-click the taskbar, and then you click Touch Keyboard on the Toolbars menu.
You call the touchable keyboard on the taskbar, and then you change the keyboard type to the third-party IME.
You double-tap the Shift key to toggle Caps Lock on.
In this scenario, Caps Lock remains in an off state.
To resolve this issue, install the December 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
See the terminology that Microsoft uses to describe software updates.