The button of the Form always be clicked by default when I press the enter key even the defaultButtonStopEvent is true.

Maybe it should add "return;" statement after "e.stopEvent();".
Same problem is also found in EXT.NET 4.1.

    clickButton : function (btn, e) {        
        if(this.defaultButtonStopEvent !== false) {
            e.stopEvent();
            // add return here?
        }
        if (btn.onClick) {
            e.button = 0;
            btn.onClick(e);
        } else {
            btn.fireEvent("click", btn, e);
        }
    }