Getting an Exception: from scene.pickSprite

i just cleaning a project and porting it to es6 synthax and I am getting an exception
Uncaught TypeError: i is undefined in the createPickingRayInCameraSpaceToRef function.

the relevant code in the project is

    let evt = pointerInfo.event;
    switch (pointerInfo.type) {
	    case BABYLON.PointerEventTypes.POINTERUP:
onClick(pointerEvt) {

     let xPos = this._scene.pointerX;
     let yPos = this._scene.pointerY;
     let pickResult = this._scene.pick(xPos, yPos);

    if (pickResult.hit){
        let pickedPoint = pickResult.pickedPoint;
        let originalPosition = new BABYLON.Vector3(pickedPoint.x, pickedPoint.y, pickedPoint.z);
        pickResult = this._scene.pickSprite(xPos, yPos);


the exception happens when calling the this._scene.pickSprite function.

Any ideas?

are you sure this is the object you think it is? It seems that this in your context is the function

I think so, yes. It is inside a class.
However I created a Playground example ( Babylon.js Playground )
Where the error is slightly different ( undefined is not an object (evaluating ‘i.update’ )= but happens also with pickSprite()

the picksprite is not registered as you have no sprite manager in the scene

thanks a lot!