Qt3d Correct rendering of transparent mesh

Question

I want to render a custom mesh (LAB.obj) with a certain transparency in a Qt3D scene. I use QDiffuseSpecularMaterial with diffuse color set to Qt.rgba(1,0.6,0.42,0.9) - alpha value is 0.9. I get strange horizontal stripes throughout my model when rendered and parts of the object which should be in the back erroneously appear in the front. See the following image:

What am I doing wrong?

Here is the code broken down to the important parts:

Item {
Scene3D {
    id: scene
    anchors.fill: parent
    aspects: ["input", "logic"]

    Entity {
        id: sceneRoot

        Camera {
            id: camera
            projectionType: CameraLens.PerspectiveProjection
            nearPlane : 0.01
            farPlane : 1000.0
            fieldOfView: 45


           position: Qt.vector3d(0,0,40)
            upVector: Qt.vector3d( 0,1,0 )
            viewCenter: Qt.vector3d(0,0,0)
        }

        OrbitCameraController {
            camera: camera
            linearSpeed: -200
            lookSpeed: -180
        }

        components: [
            RenderSettings {
                 ForwardRenderer {
                    camera: camera
                    clearColor: "transparent"
                }
            },
            InputSettings {}
        ]

        Entity {
            id: customEntity

            components: [
                DiffuseSpecularMaterial {
                    diffuse: Qt.rgba(1,0.6,0.42,0.9)
                    alphaBlending:true
                },
                Mesh {
                    id: customMesh
                    source: "qrc:LAB"
                }
            ]
        }

    }



}

}