Cannot get patch to work - throws: Failed to dereference pointer

[npfrizze]

I have 2 json files that I Diff to produce a PatchDocument. I want to get a string representation of the difference so I can store it for use later to regenerate a json file using the original json and the patch. Here is the code

        JsonDiffer jsonDiff = new JsonDiffer();
       JsonPatcher patcher = new JsonPatcher();
        try { 
            string modifiedJson = File.ReadAllText($"c:/temp/modified.json");
            string defaultJson = File.ReadAllText($"c:/temp/default.json");
            PatchDocument patch = jsonDiff.Diff(defaultJson, modifiedJson, true);
            JToken defJson = JToken.Parse(defaultJson);
            patcher.Patch(ref defJson, patch);  // works

            Console.WriteLine(defJson);

            // get a string from PatchDocument - so I can save it for  later and then patch original json
            var patchString= patch.ToString(Newtonsoft.Json.Formatting.None);
            Console.WriteLine(JToken.Parse(patchString));
            // take that string and create a PatchDocument so it can be patched with original json
            var patchDoc = PatchDocument.Parse(patchString);
            defJson = JToken.Parse(defaultJson);
            patcher.Patch(ref defJson, patchDoc);  // this throws - Failed to dereference pointer

            // Also tried creating PatchDocument using stream
            System.IO.MemoryStream mStream = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(patchString));
            patchDoc = PatchDocument.Load(mStream);
            patcher.Patch(ref defJson, patchDoc);  // this throws - Failed to dereference pointer

            // Also tried getting string from PatchDocument using ToStream
            var outputstream = patch.ToStream();
            patchString = new StreamReader(outputstream).ReadToEnd();
            Console.WriteLine("stream" + patchString);
            mStream = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(patchString));
            patchDoc = PatchDocument.Load(mStream);
            patcher.Patch(ref defJson, patchDoc);  // this throws - Failed to dereference pointer

            // take that string and create a PatchDocument so it can be patched with original json
            patchDoc = PatchDocument.Parse(patchString);
            patcher.Patch(ref defJson, patchDoc);  // this throws - Failed to dereference pointer

The problem seems to be when I generate the string from the PatchDocument and/or use that string to build a PatchDocument. What am I doing wrong?

Attached is the json.
modified.txt
default.txt