Inverse Kinematics in Arkit - ios

Question

I have Scenekit model with 4 joints.
When I use it in SCNView with the code below and change the position of the parent node (Joint) I can see it animated according to the joints.
private lazy var scene: SCNScene = {
let scene = SCNScene(named: "art.scnassets/ears")!
return scene
}()
in viewDidLoad
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3(x: 0, y: 0, z: 5)
rootNode.addChildNode(cameraNode)
scnView.scene = scene
scnView.allowsCameraControl = true
scnView.backgroundColor = .white
let joint = contentNode!.childNode(withName: "Joint", recursively: true)!
var ik:SCNIKConstraint = .inverseKinematicsConstraint(chainRootNode: joint)
joint.childNode(withName: "head", recursively: true)!.constraints = [ik]
The problem occurs when I use the same model in Arkit. In this case, I use a separate View Controller than above. I place it on the head. The model collapse when I show it in Arkit with the code below. I expect it to track head movement and bend according to it.
func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
guard let sceneView = renderer as? ARSCNView,
anchor is ARFaceAnchor else { return nil }
faceGeometry = ARSCNFaceGeometry(device: sceneView.device!)!
contentNode = SCNReferenceNode(named: "art/ears")
//contentNode!.physicsBody = .kinematic()
let joint = contentNode!.childNode(withName: "Joint", recursively: true)!
var ik:SCNIKConstraint = .inverseKinematicsConstraint(chainRootNode: joint)
joint.childNode(withName: "head", recursively: true)!.constraints = [ik]
return contentNode
}
I have this extension
extension SCNReferenceNode {
convenience init(named resourceName: String, loadImmediately: Bool = true) {
let url = Bundle.main.url(forResource: resourceName, withExtension: "scn", subdirectory: "Models.scnassets")!
self.init(url: url)!
if loadImmediately {
self.load()
}
}
Normal look of model is like this
Correctly applied inverse kinematics snapshot
I tried setting setMaxAllowedRotationAngle(between 20-45 degrees) to the joints, this prevents collapse behavior but it also prevents bending.
y property of model gravity is -9.8, x and z are 0.
What might be the problem that I can't create the same effect in Arkit?