When I try to maximize a window on any screen other than my primary, while the screen arrangement is anything other than Left<>Right edge aligned, windows only maximize to half screen.
see screen shot.
In this example I have my monitors arranged in a triangle. When I arrange them in a straight line maximize works fine. The behavior is the same whether I max by double-clicking title bar, dragging to top of screen, or clicking arrows on the top right of the window.