Dialog will disable Shortcut in it's parent?

I have a dialog in my main.qml file the problem is that when I click menu to open dialog, after closing the dialog, Shortcut don't work any more.

main.qml

ApplicationWindow {
    id:mainWindow

    Shortcut {
        id:backShortcut
        sequences: ["Esc", "Back"]
        onActivated: {
            console.log("Back In MainPage")
            if(sv.depth>1)
            {
                sv.pop();
            }
            else if(drawer.visible){
                drawer.close();
            }
            else{
                exitDialog.open();
            }
        }
    }

    MenuItem{
        contentItem: Text {
              text: qsTr("Open Dialog")
        }
        onClicked: {
              var c= myDialogCom.createObject(mainWindow);
              c.open();
        }
    }

    Component{
        id:myDialogCom
        MyDialog{
        }
    }
}

MyDialog.qml

Dialog {
    id: root

    parent: Overlay.overlay
    x:0
    height: mainWindow.height
    width:mainWindow.width

    header: ToolBar{
    }

    StackView{
    }

}

Edit I want to mention that I have summarized my questions for a faster understanding.But I had multiple Shortcut in diffrent pages like:(ChatsPage.qm and ChatPage.qml and main.qml) but tried to question be simple,So I just said Shortcut in just main.qml becuase the problem is there yet

I changed context property of Shortcut to Qt.ApplicationShortcut .Now It works.But I don't know why :> ,tanks if every body explain

Shortcut {
        id:backShortcut
        sequences: ["Esc", "Back"]
        context: Qt.ApplicationShortcut
        onActivated: {
            console.log("Back In MainPage")
            if(sv.depth>1)
            {
                sv.pop();
            }
            else if(drawer.visible){
                drawer.close();
            }
            else{
                exitDialog.open();
            }
        }
    }