imac: keyboard stuck on caps lock From time to time the (Apple USB) keyboard of my imac (21.5-inch, Mid 2010, mac os 10.12.5) gets stuck on caps lock (namely all letters are printed capital, and I can't turn capital off), and I have to unplug the USB cable to fix this; when I plug it back, the light is on, and I can turn caps lock off. This happens more frequently after installing mac os updates, then it gradually becomes less frequent.

Are there an explanation and a solution for this issue?
Just unplug the USB from the back of your computer. Plug the USB back into the computer. Solved.