Since updating my computer to Mavericks all my commands have gone wonky.
My main key problem is my left command key. The right one works correctly with all the shortcuts I use, but the left one zooms out the screen and puts similar applications side by side.
I've tried a lot with System Preferences but since I am new to Mavericks it's hard to find what I am looking for.
Go to System Preferences > Mission Control and check the shortcut for Application windows. It must be set on the left ⌘ key (this must be the only OS X section that accepts single modifier keys).
Mission Control http://cdn.mactrast.com/wp-content/uploads/2013/10/Mission_Control-582x480.png
I had the same problem. At first I didn't have a problem until I chose Restore Defaults in the keyboard menu shortcuts. From that moment I had the same problem with the left command key.
I checked Mission Control and the command-left keyboard shortcut was not selected, so I didn't see any problem there but just to make sure I selected every shortcut again and the problem is gone.
What worked for me was selecting and deselecting the Applications Windows piece as noted above.
BTW, this also affected my Right Shift key, but the solution got both in one shot.
I am running macOS High Sierra 10.13.4.
