ElasticSearch Search Query and Highlight on the Attachment not working as expected


I am New to ES, i am trying to index a complete text file in ES. i am using ElasticSearch 2.3.3 with attachment Plugin (mapper-attachement-2.3.3). i am able to index the document(of size 613KB) without any error.
Below are code snippets

public class Document1
    public Document1()


    public string Title { get; set; }

    [Attachment(Name = "file")]
    public Attachment File { get; set; }    

Index creation:

var mappingResponse = client.CreateIndex(index, c => c
.Mappings(m => m
.Map(mm => mm.AutoMap())

indexing a File.
var attachment = new Attachment();
attachment.Content = Convert.ToBase64String(File.ReadAllBytes(path));
attachment.ContentType = "plain/txt";
attachment.Name = "XA121026_2014_06_09_AXIS_ERR.txt";

        var doc = new Document1()
             Title = "XA121026_2014_06_09_AXIS_ERR.txt",
             File = attachment

         var i =  client.Index<Document1>(doc);

and the Mapping looks like


I have two issues.

  1. I am able to search strings until certain part of the documents, for the strings in the middle and end of the documents returns ZERO hits.

  2. Highlighting does not work for me.

The Search query is

          var queryString1 = "CapUpdateRequest";

            var searchRes = client.Search<Document1>(s => s
                .Query(qs => qs.QueryString(q => q.Query(queryString1)))
                .Highlight(h => h                        
                f => f.Field(e => e.File)                    

Am i missing something, try to get a break from last couple of days.