CharacterController movement messed up when Y Center is larger than radius

The CharacterController.Move function produces erratic results ( slipping/sliding jittering movement struggling to move in the correct direction ) when the y center is offset to more than the capsule radius. Unity 5.6.1f1

I'd supply an image but your image upload doesn't work ( Firefox 54.0.1 (32-bit) )

 using UnityEngine;
 
 namespace MyNamespace
 {
     public class TestController : MonoBehaviour
     {
         public CharacterController _controller;
         public Animator _animator;
         public Transform _transform;
 
         Vector3 _deltaPosition = Vector3.zero;
 
         void Start()
         {
             _deltaPosition = Vector3.zero;
         }
         
         void Update()
         {
             _animator.SetFloat( "Horizontal", Horizontal );
             _animator.SetFloat( "Z", Horizontal );
             _animator.SetFloat( "InputMagnitude", Mathf.Abs( Horizontal ) );
             _animator.SetBool( "IsStopLU", true );
 
             _controller.Move( _deltaPosition );
         }
 
         public float Horizontal
         {
             get{ return Input.GetAxis( "Horizontal" ); }
         }
 
         void OnAnimatorMove()
         {
             _deltaPosition = _animator.deltaPosition;
             Debug.Log( "_deltaPosition " + _deltaPosition / Time.deltaTime );
         }
         
     }
     
 }

Using Kubold's Sword animator controller and animations, no rigid body. The erratic movement increases in intensity relative to the amount the CharacterController capsule Y center's offset is over/larger than/above the CharacterController capsule's radius