Custom Inspector, variable updating problem

Hi all, I have a problem with a CustomEditor that is driving me crazy... I have a class named WaveformGenerator that generates sound given a specific waveform, with a type (sinus, triangle, custom, etc.) a frequency and a gain. I have a CustomEditor for this class, WaveformGeneratorEditor, that allows me to select and display the waveform. Here is a picture :

I want to change the display of the curve when I change the type of my waveform. Also, if I change manually the curve, I want my waveform type to change automatically to "custom".

My CustomEditor is supposed to do that, here is the code :

 public override void OnInspectorGUI() {
         WaveformGenerator generator = (WaveformGenerator)target;
 
         EditorGUILayout.PropertyField(serializedObject.FindProperty("active"));
         EditorGUILayout.PropertyField(serializedObject.FindProperty("type"));
         EditorGUILayout.PropertyField(serializedObject.FindProperty("waveform"));
 
         //If my waveform type has changed, update the curve
         if ((int)generator.type != generator.PreviousWaveformTypeIndex) {
             Waveform waveform = Waveform.GetFromType(generator.type);
             if (waveform != null) {
                 waveform.Init(generator.waveform.gain, generator.waveform.frequency);
                 generator.waveform = waveform;
                 int resolution = 64;
                 float[] signal = generator.waveform.GetWaveformSample(resolution);
                 Keyframe[] keys = new Keyframe[signal.Length];
                 for (int i = 0; i < signal.Length; i++) {
                     keys[i] = new Keyframe(2 * Mathf.PI * i / (float)resolution, signal[i]);
                 }
                 generator.PredefinedCurve = new AnimationCurve(keys);
                 generator.CurrentCurve = new AnimationCurve(keys);
                 generator.PreviousWaveformTypeIndex = (int)generator.type;
             }
         }
 
         generator.CurrentCurve = EditorGUILayout.CurveField(generator.CurrentCurve, GUILayout.Height(50));
 
         //If curve has been changed manually, change the waveform type to "custom"
         if (!generator.CurrentCurve.keys.SequenceEqual(generator.PredefinedCurve.keys)) {
             generator.type = WaveformType.Custom;
             Waveform waveform = new CustomWaveform(GetValuesFromKeys(generator.PredefinedCurve.keys));
             waveform.Init(generator.waveform.gain, generator.waveform.frequency);
             generator.waveform = waveform;
             generator.PredefinedCurve.keys = generator.CurrentCurve.keys;
             generator.PreviousWaveformTypeIndex = (int)generator.type;
         }
 
         serializedObject.ApplyModifiedProperties();
         if (GUI.changed)
             EditorUtility.SetDirty(target);
     }

In this code, you can see that I modify some variables of my WaveformGenerator. Those variables are declared as follows :

     [SerializeField]
     int previousWaveformTypeIndex = -1;
     public int PreviousWaveformTypeIndex { get { return previousWaveformTypeIndex; } set { previousWaveformTypeIndex = value; } }
     [SerializeField]
     AnimationCurve currentCurve = new AnimationCurve();
     public AnimationCurve CurrentCurve { get { return currentCurve; } set { currentCurve = value; } }
     [SerializeField]
     AnimationCurve predefinedCurve = null;
     public AnimationCurve PredefinedCurve { get { return predefinedCurve; } set { predefinedCurve = value; } }

I have two problems with this :

1) when I modify the type of my waveform in the inspector, sometimes the curve is not updated. For instance if I go from Sinus to Sawtooth everything works well, but if I go back to Sinus, my curve stays on Sawtooth. I don't understand why !!

2) when I modify manually the curve, the type variable is changed to custom, but the change is not display in the inspector. For instance if I modify manually the Sinus curve, the type is changed to Custom in my class (I checked with a print), but the inspector tells me I'm still on a Sinus.

Any idea ? If you need any additional information please ask me.

Thanks !