ARSCNView.pointOfView.position contains NaN in x, y, z

Hi,

I'm building SceneKit app and run into a weird situation. From time to time, I can 't see any virtual objects in AR Scene, but it works perfectly in most cases. And in this moment I can't see any objects, sceneView.pointOfView.position.x or y or z is Nan, rotation is the same.

    guard let camera = sceneView?.pointOfView else {
      print("Get phonePosition Fail")
      return nil
    }
     
    // TODO: Don't know why sceneView?.pointOfView gets nothing (NaN). Should find out why.
    if camera.position.x.isNaN {
      if let session = sceneView?.session {
        interrupted?(session)
      }
      return nil
    }

Did anyone handle this case before?