PySide: AnchorChanges in state transmission not working

DaGSE

Hello,

I'm trying to animate an BorderImage element with two states (shown, hidden) using AnchorChanges.
But everytime the state transmission should be performed PySide prints the following error:
Unable to assign QObject* to QDeclarativeItem*
(this seems to belong to the target property, since with commenting it the error disappears but then no animation is shown)

Sample code as follows:
@BorderImage {
id: screenKeyboard

state: "hidden"

states: [
    State {
        name: "shown"
        AnchorChanges {
            target: screenKeyboard
            anchors.top: undefined
            anchors.bottom: menuBar.top
        }
    },
    State {
        name: "hidden"
        AnchorChanges {
            target: screenKeyboard
            anchors.top: menuBar.top
            anchors.bottom: undefined
        }
        StateChangeScript {
            name: "resetKeyboard"
            script: {keyColumn.state = "default";}
        }
    }
]

transitions: [
    Transition {
        from: "shown"; to: "hidden"
        SequentialAnimation {
            AnchorAnimation { easing.type: Easing.OutQuart; duration: 300 }    
            ScriptAction { scriptName: "resetKeyboard" }
        }
    },
    Transition {
        from: "hidden"; to: "shown"   
        AnchorAnimation { easing.type: Easing.OutQuart; duration: 300 }

PropertyAnimation {target: screenKeyboard; property: "opacity"; to: 1; duration: 250}
}
]
@

I did not find any helpful hints for the error on the internet so hopefully you can help me (I'm pretty sure the same Qml code worked with C++ Qt)