Is there a lot of difference in "binary writing" of a file when entering lists or dictionaries?

I'm developing a project in language C# where I need to use files to save the data that circulates in data structures.

It turns out that I had the whole project badly drawn, I was not programming in layers. I was previously using Lists (data structure) and to write the Data the methods below are working perfectly

 public static bool GravaCarrosEstacionados(string filename,Dictionary<string,Park> carros)
        {

            try
              {
                 Stream stream = File.Open(filename, FileMode.Create);
                 BinaryFormatter bin = new BinaryFormatter();
                 bin.Serialize(stream, carros);
                 stream.Close();
                 return true;
              }
              catch (IOException e)   
              {
                  Console.Write("ERRO:" + e.Message);
                  return false;
              }
        }


 public static bool CarregarCarrosEstacionados(string fileName,string nomeP)
        {
            if (File.Exists(fileName))
            {
                try
                {
                    Stream stream = File.Open(fileName, FileMode.Open);
                    BinaryFormatter bin = new BinaryFormatter();
                    parques = (Dictionary<string,Park>)bin.Deserialize(stream);
                    stream.Close();

                    foreach (KeyValuePair<string, Park> x in parques)
                    {
                        if (parques.ContainsKey(nomeP))
                        {
                            Console.WriteLine("Carro {0}", x.Value.Carro.Marca);
                            Console.WriteLine("Modelo {0}", x.Value.Carro.Modelo);
                            Console.WriteLine("Matricula {0}", x.Value.Carro.Matricula);


                        }

                    }

                }
                catch (IOException e)
                {
                    Console.Write("ERRO:" + e.Message);
                    return false;
                }


            }
            return true;

        }

Obviously I applied lists instead of dictionaries during "serialize" and "Deserialize" . Now with the dictionary when adding a car to the system for example, I can not even save the file.

What could be happening differently?