Xamarin iOS Monogame app losing data

Hi all,
I wrote a Xamarin Monogame app which I currently test on my iPad. I have noticed that my app loses its app data after each restart (whether forced or by staying in background for a long time). I followed the tutorials, I tried saving to the Documents/ and Library/ folders but no luck. Any suggestions?

        private string _historyFilePath = Path.Combine(MariasekMonoGame.ConfigPath, "Mariasek.history");
        //...
        public static string ConfigPath
        {
            get
            {
                #if __IOS__
                var personalPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);

                return Path.Combine(personalPath, "..", "Library");
                #else
                return Environment.GetFolderPath(Environment.SpecialFolder.Personal);
                #endif
            }
        }
        //...
        public void SaveHistory()
        {
            var xml = new XmlSerializer(typeof(List<HistoryData>));
            try
            {
                using (var fs = File.Open(_historyFilePath, FileMode.Create))
                {
                    xml.Serialize(fs, Game.Money);
                }
            }
            catch(Exception e)
            {
                System.Diagnostics.Debug.WriteLine(string.Format("Cannot save history\n{0}", e.Message));
            }
        }