////main.qml
import QtQuick 2.4

Item {
    id: root

    property real someProperty

    Inner {
        //the existence of this property triggers the bug
        property bool iDoAbsolutelyNothing

        Component.onCompleted: {
            console.log("Changing someValue indirectly - this doesn't trigger the behavior");
            root.someProperty = 1
            console.log("Changing someValue directly - this triggers the behavior");
            someValue = 2
        }

        someValue: root.someProperty
    }
}

//// Inner.qml
import QtQuick 2.4

Item {
    property real someValue

    onSomeValueChanged: console.log("someValue changed to", someValue);
    Behavior on someValue {
        ScriptAction { script: { console.log("someValue Behavior triggered"); }}
    }
}