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System.Exception: Failed migrating [Umbraco.NestedContent - achievementsList] : Additional text encountered after finished reading JSON content: [. Path '', line 20, position 1.
 ---> Newtonsoft.Json.JsonReaderException: Additional text encountered after finished reading JSON content: [. Path '', line 20, position 1.
   at Newtonsoft.Json.JsonTextReader.Read()
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at uSync.Migrations.Migrators.Optional.NestedToBlockListMigrator.GetContentValue(SyncMigrationContentProperty contentProperty, SyncMigrationContext context)
   at uSync.Migrations.Handlers.Shared.SharedContentBaseHandler`1.MigrateContentValue(SyncMigrationContentProperty migrationProperty, SyncMigrationContext context)
   at uSync.Migrations.Handlers.Shared.SharedContentBaseHandler`1.ConvertPropertyValue(String itemType, String contentType, XElement property, SyncMigrationContext context)
   --- End of inner exception stack trace ---
   at uSync.Migrations.Handlers.Shared.SharedContentBaseHandler`1.ConvertPropertyValue(String itemType, String contentType, XElement property, SyncMigrationContext context)
   at uSync.Migrations.Handlers.Shared.SharedContentBaseHandler`1.MigrateFile(XElement source, Int32 level, SyncMigrationContext context)
   at uSync.Migrations.Handlers.MigrationHandlerBase`1.MigrateFolder(String folder, Int32 level, SyncMigrationContext context)