I had previously reported an issue with my middle button that I thought was related to new app configurations. I think this is still an issue, but I have the same issue just when switching applications. I will set the middle button to 'show/hide desktop', and it will work. But then I switch to the Chrome application and it stops working, and I have to reset it. If I switch to Chrome via command+tab (instead of clicking), the first click will show the desktop, but subsequent clicks will not hide the desktop.