Unity中SerializeReference的Redo功能失效问题求助

我正在利用UI Elements的PropertyField类制作PropertyDrawer，设置了下拉菜单用于选择平滑算法类型。目前Undo功能正常，但Redo功能完全失效。我尝试了Undo类的多种方法（比如FlushUndoRecordObjects、IncrementCurrentGroup、RecordObject），但Redo始终无法触发。

示例截图 #

• 第一种平滑类型
  
• 第二种平滑类型
  

相关代码 #

using System;
using UnityEditor;
using UnityEditor.UIElements;
using UnityEngine;
using UnityEngine.UIElements;

namespace Whatever
{
    public class SmoothingTest : MonoBehaviour
    {
        public Smoothing Smoothing;
    }

    [Serializable]
    public sealed class Smoothing
    {
        [SerializeField]
        internal SmoothingType MethodType;

        [SerializeReference]
        internal SmoothingMethod Method = new SmoothingMethodExponentialSingle();

        public float Smooth(float value)
        {
            return Method.Smooth(value);
        }
    }

    [CustomPropertyDrawer(typeof(Smoothing))]
    internal sealed class SmoothingDrawer : PropertyDrawer
    {
        public override VisualElement CreatePropertyGUI(SerializedProperty property)
        {
            var pf = new PropertyField(property, preferredLabel);

            var sp = property.FindPropertyRelative(nameof(Smoothing.MethodType));

            pf.TrackPropertyValue(sp, OnMethodTypeChanged);

            return pf;
        }

        private static void OnMethodTypeChanged(SerializedProperty property)
        {
            var parent = property.GetParentProperty();

            var method = parent.FindPropertyRelative(nameof(Smoothing.Method));

            var type = (SmoothingType)property.intValue;

            method.managedReferenceValue = type switch
            {
                SmoothingType.ExponentialSingle => new SmoothingMethodExponentialSingle(),
                SmoothingType.ExponentialDouble => new SmoothingMethodExponentialDouble(),
                _                               => throw new NotSupportedException(type.ToString())
            };

            method.serializedObject.ApplyModifiedProperties();
        }
    }

    public static class SerializedPropertyExtensions // TODO move
    {
        public static SerializedProperty GetParentProperty(this SerializedProperty property)
        {
            var path = property.propertyPath;

            var last = path.LastIndexOf('.');

            path = path[..last];

            var prop = property.serializedObject.FindProperty(path);

            return prop;
        }
    }

    public enum SmoothingType
    {
        ExponentialSingle,
        ExponentialDouble
    }

    [Serializable]
    public abstract class SmoothingMethod
    {
        [SerializeField]
        private float Last;

        public float Smooth(float value)
        {
            Last = SmoothCore(value, Last);
            return Last;
        }

        protected abstract float SmoothCore(float value, float last);
    }

    [Serializable]
    public sealed class SmoothingMethodExponentialSingle : SmoothingMethod
    {
        public float Alpha;

        protected override float SmoothCore(float value, float last)
        {
            // https://en.wikipedia.org/wiki/Exponential_smoothing#Basic_(simple)_exponential_smoothing
            return Alpha * value + (1 - Alpha) * last;

            // https://en.wikipedia.org/wiki/Exponential_smoothing#%22Exponential%22_naming
            return last + Alpha * (value - last);
        }
    }

    [Serializable]
    public sealed class SmoothingMethodExponentialDouble : SmoothingMethod
    {
        public float Alpha;
        public float Beta;
        public float BetaLast; // TODO private

        protected override float SmoothCore(float value, float last)
        {
            // https://en.wikipedia.org/wiki/Exponential_smoothing#Double_exponential_smoothing_(Holt_linear)
            var st = Alpha * last + (1 - Alpha) * (last + BetaLast);
            var bt = Beta * (st - last) + (1 - Beta) * BetaLast;
            BetaLast = bt;
            return st;
        }
    }
}

内容的提问来源于stack exchange，提问作者aybe