UNITY Humanoid型　rig情報が崩れる

Humanoid型に設定した3DモデルをResources.Loadを使って読み込むとAnimatorのAvatar項目にはmodelAvatarと表示されるのですが、

UnityEngine.Object modelPrefab = Resources.Load(modelPath + "/model", typeof(GameObject));	
GameObject selModels = (GameObject)GameObject.Instantiate(modelPrefab, Vector3.zero, Quaternion.Euler(0, 180f, 0));

TriLibを使って下記のように読み込むと下記画像のようにAnimatorのAvatar項目がnullになってしまいます。

GameObject selModels;

using (var assetLoader = new AssetLoaderAsync())
{
    var assetLoaderOptions = AssetLoaderOptions.CreateInstance();
    assetLoaderOptions.RotationAngles = new Vector3(0f, 180f, 0f);
    assetLoaderOptions.AutoPlayAnimations = true;
    assetLoader.LoadFromFile(modelPath, assetLoaderOptions, null, delegate (GameObject loadedGameObject)
    {
        selModels = loadedGameObject;
                
        Animator _animator = selModels.GetComponent<Animator>();
        if (_animator == null)
        {
            _animator = selModels.AddComponent<Animator>();
            _animator.avatar = null;                            //???
            _animator.applyRootMotion = true;
            _animator.updateMode = AnimatorUpdateMode.Normal;
            _animator.cullingMode = AnimatorCullingMode.CullUpdateTransforms;
        }
     });
}