Weird NSToolbar Bug

[hazkid]

I have a simple app with an NSToolbar that switches between views of different sizes. Everything works fine, including animations and window resizing, but when the upper-right button (pill shaped) is clicked, the metal toolbar background and the bottom window edge slide up. This leaves the toolbar items floating under the title bar, disabled, while the bottom of the view is clipped. I really have no idea what is going on here.