Partial Search in elasticsearch is working for one and not for other record

elastic search is created with following body

body = {
        "mappings": {
            "properties": {
                "TokenizedDocumentFileName": {
                    "type": "text",
                    "analyzer": "my_analyzer",
                    "search_analyzer": "standard"
                }
            }
        },
        "settings": {
            "analysis": {
                "analyzer": {
                    "my_analyzer": {
                        "tokenizer": "keyword",
                        "filter": ["word_delimiter",
                                   "lowercase"
                                   ]
                    }
                }
            },
            "number_of_shards": "1",
            "number_of_replicas": "0"
        }
    }

Now there below is 2 different metadata in elasticsearch

{'_index': 'fileboundunitmanuals',
 '_type': '_doc',
 '_id': '997439.PDF',
 '_version': 2,
 '_seq_no': 166958, 
 '_primary_term': 1,
 'found': True, '_source': {
 'IndexKey': '997439.PDF',
 'DocumentID': 997439,
 'Extension': 'PDF',
 'FileID': 174508,
 'DocumentFileName': '\\UNIT xxxxx\\411xxx\\A9.xxxx_xxxxx GAS ENGINE xxxxx_x_997439.PDF',
 'TokenizedDocumentFileName': '\\UNIT xxxxx\\411xxx\\A9. xxxx xxxxx GAS ENGINE xxxxx x 997439.PDF',
 'F1': 'UNIT xxxxx', 
 'ProjectID': 8}}  

2nd record

 {'_index': 'fileboundunitmanuals',
  '_type': '_doc',
  '_id': '3929829.pdf',
  '_version': 1,
  '_seq_no': 538517,
  '_primary_term': 3, 
  'found': True, '_source': {
  'Extension': 'pdf', 
  'DocumentID': 3929829,
  'IndexKey': '3929829.pdf',
  'FileID': '',
  'DocumentFileName': '\\Unit xxxxx\\Mary Testing\\marynewfiletest.pdf', 
  'TokenizedDocumentFileName': '\\Unit xxxxx\\Mary Testing\\marynewfiletest.pdf',
  'F1': 'Unit xxxxx',
  'ProjectID': 8}}

now when searching in elasticsearch using following query for 1st record

  {
  "query":{
  "bool":{
     "must":{
        "match":{
           "TokenizedDocumentFileName":{
              "query":"997439"
           }
        }
     },
     "filter":{
        "bool":{
           "must":[
              {
                 "term":{
                    "ProjectID":8
                 }
              },
              {
                 "term":{
                    "Extension":"pdf"
                 }
              }
           ]
        }
     }
  }
  }
  }

query to search for 2nd record

  {
  "query":{
  "bool":{
     "must":{
        "match":{
           "TokenizedDocumentFileName":{
              "query":"marynewfiletest"
           }
        }
     },
     "filter":{
        "bool":{
           "must":[
              {
                 "term":{
                    "ProjectID":8
                 }
              },
              {
                 "term":{
                    "Extension":"pdf"
                 }
              }
           ]
        }
     }
  }
  }
  }

first query is giving me the right result , since query "997439" is present in TokenizedDocumentFileName , but when I am searching marytesting for 2 records I am getting following respone.

{'took': 0, 'timed_out': False, '_shards': {'total': 1, 'successful': 1, 'skipped': 0, 'failed': 0}, 'hits': {'total': {'value': 0, 'relation': 'eq'}, 'max_score': None, 'hits': []}}

But when I am giving filename along with extension i.e "marytesting.pdf", in this case I am getting the right result.

OUTPUT of GET fileunitmanuals

{
"fileboundunitmanuals" : {
"aliases" : { },
"mappings" : {
  "properties" : {
    "DocumentFileName" : {
      "type" : "text",
      "analyzer" : "my_analyzer",
      "search_analyzer" : "standard"
    },
    "DocumentID" : {
      "type" : "long"
    },
    "Extension" : {
      "type" : "text",
      "fields" : {
        "keyword" : {
          "type" : "keyword",
          "ignore_above" : 256
        }
      }
    },
    "F1" : {
      "type" : "text",
      "fields" : {
        "keyword" : {
          "type" : "keyword",
          "ignore_above" : 256
        }
      }
    },
    "FileID" : {
      "type" : "long"
    },
    "IndexKey" : {
      "type" : "text",
      "fields" : {
        "keyword" : {
          "type" : "keyword",
          "ignore_above" : 256
        }
      }
    },
    "ProjectID" : {
      "type" : "long"
    },
    "TokenizedDocumentFileName" : {
      "type" : "text",
      "fields" : {
        "keyword" : {
          "type" : "keyword",
          "ignore_above" : 256
        }
      }
    }
  }
},
"settings" : {
  "index" : {
    "number_of_shards" : "1",
    "provided_name" : "fileboundunitmanuals",
    "creation_date" : "1607069298331",
    "analysis" : {
      "analyzer" : {
        "my_analyzer" : {
          "filter" : [
            "word_delimiter",
            "lowercase"
          ],
          "tokenizer" : "keyword"
        }
      }
    },
    "number_of_replicas" : "0",
    "uuid" : "u8HasYfVT6iMr7XGpdjJHg",
    "version" : {
      "created" : "7090199"
    }
  }
}
}
}

So the question is why partialsearch is working for the 1st one and not for the second one.

According to your mapping, the field TokenizedDocumentFileName is just text and keyword, so it doesn't have your analyzers. So it's just a coincidence that your first query works.

You should make sure to properly create your index with the right mapping before indexing your first document.

PS: I was able to create your index with the settings/mappings you gave and I got the expected result for the both queries, so you're almost there.