Elasticsearch multi level nested query

Hi,

Having a mapping with multi level nested fields like this:

{
  nestedField: {
    type: "nested",
    include_in_parent: true,
    multiple: true,
    properties: {
      province: {
        type: "nested",
        include_in_parent: true,
        multiple: true
      },
      properties: {
        comuni: {
          type: "nested",
          include_in_parent: true,
          multiple: true,
          properties: {
            nome: {
              type: "string"
            },
            parziale: {
              type: "boolean"
            }
          }
        },
        nome: {
          type: "string"
        }
      }
    }
  },
  regione: {
    type: "string"
  }
}

documentation: https://www.elastic.co/guide/en/elasticsearch/reference/1.7/query-dsl-nested-query.html.

query:

{
  "size": 1,
  "version": true,
  "query": {
    "filtered": {
      "query": {
        "function_score": {
          "query": {
            "bool": {
              "must": [
                {
                  "regex_term": {
                    "field_2": {
                      "term": ".*701.*",
                      "ignorecase": true
                    }
                  }
                }
              ]
            }
          },
          "functions": [
            {
              "script_score": {
                "script": "_score * -doc['field_2'].value.length()"
              }
            }
          ]
        }
      },
      "filter": {
        "nested": {
          "path": "nestedField",
          "filter": {
            "bool": {
              "must": [
                {
                  "term": {
                    "nestedField.regione": "Lazio"
                  }
                },
                {
                  "bool": {
                    "must": [
                      {
                        "or": {
                          "filters": [
                            {
                              "term": {
                                "nestedField.province.nome": "Pordenone"
                              }
                            },
                            {
                              "not": {
                                "filter": {
                                  "exists": {
                                    "field": "nestedField.province.nome"
                                  }
                                }
                              }
                            }
                          ]
                        }
                      },
                      {
                        "or": {
                          "filters": [
                            {
                              "term": {
                                "nestedField.province.comuni.nome": "Udine"
                              }
                            },
                            {
                              "not": {
                                "filter": {
                                  "exists": {
                                    "field": "nestedField.province.comuni.nome"
                                  }
                                }
                              }
                            }
                          ]
                        }
                      }
                    ]
                  }
                }
              ]
            }
          }
        }
      }
    }
  }
}

The data look like this:

{
  "_source": {
    "otheFields" ...,
    "nestedField": [
      {
        "regione": "Lazio"
      },
      {
        "province": [
          {
            "nome": "Venezia"
          },
          {
            "nome": "Treviso"
          }
        ],
        "regione": "Veneto"
      },
      {
        "province": [
          {
            "comuni": [
              {
                "nome": "Varmo",
                "parziale": false
              }
            ],
            "nome": "Udine"
          }
        ],
        "regione": "Friuli venezia giulia"
      }
    ]
  }
}

The query doesn't find the given record even if the province field is missing, instead it work fine if we use "Veneto" for regione and "Treviso" for provincia.nome and also using the comune field in the other nested object.

Why this query doesn't work ?