Mac OS X - Main menu items unresponsive

When I start Gmod on my mac, the main menu loads in no time, but the menu items are not responsive. It acts just like a static image.
I found a fix that worked until I moved the window. I went in Window and selected Garry’s mod, which was unchecked. Then the menu became responsive again. But then I moved the window to my second monitor and the menu became frozen once again. It seems like focusing on something outside the game, be it the window bar or the window of another application will cause the menu to become frozen when gmod is refocused.