The mesh from polylineVolume

When I set imageMaterial to the PolylineVolumeGraphics, the top face of mesh is broken. How to set texture to the top face ?

textture(LuZhuang.jpg):

Result:

computeRectangle(width: number, height: number) {
    var positions = [];
    width *= 0.5;
    height *= 0.5;

    positions.push(new Cesium.Cartesian2(-width, height));
    positions.push(new Cesium.Cartesian2(width, height));

    positions.push(new Cesium.Cartesian2(width, -height));

    positions.push(new Cesium.Cartesian2(-width, -height));
    return positions;
}
createEntity() {
    if (this.data.positions.length > 1) {
        let polylineVolume = new Cesium.PolylineVolumeGraphics({
            positions: this.data.positions,
            shape: this.computeRectangle(2, 0.2),
            material: new Cesium.ImageMaterialProperty({
                image: "assets/material/LuZhuang.jpg"
            })

        })
        this.entity = new Cesium.Entity({
            position: this.data.positions[0],
            polyline: lineData,
            polylineVolume: polylineVolume,
        })
        PathTool.instance.viewer.entities.add(this.entity);
    }
}