Reflection: "Field items defined on type Inventory is not a field on the target object which is of type PartyManager"

I need to make use of dictionaries in the editor, so I made my own editable Dictionary class based on parallel lists, with it's own editor script. When I make us of this script on some string->int, string->bool, and string->string dictionaries in a component, it works fine.

However, I also have a component`PartyManager` which has a member parties , which is a List<Party>. Party objects have a member inventory, which is of type Inventory, which wraps around a EditableDictionary<InventoryItem,int> member called items, where InventoryItem is a ScriptableObject.

When I inspect the PartyManagerobject, I reciever the error "Field items defined on type Inventory is not a field on the target object which is of type PartyManager". The error points towards the function

 private void InitDict(SerializedProperty dictionary) {
         if (dict == null) {
             dict = fieldInfo.GetValue(dictionary.serializedObject.targetObject) as EditableDictionary<TK, TV>;
         }
     }

dict in this case is a member of the editor script that points to the underlying EditableDictionary object.

How can I avoid this issue, and is there an explanation as to why this occurs only when the dictionary is under several layers of objects? My understanding is that fieldInfo here points to the component and thus I need to find the holding object rather than the parent component.

Thanks in advance for any help.