Filter in aggregation not working with top hits

Hello,
I'm trying to write a query to form an aggregation of all the colleges under a university, put them into country id buckets and get the top colleges based out of each country.

Somehow I'm not getting what I'm expecting as its not filtering based on "university.id" and not creating the buckets on country.fid
The same query works for ES v5.3.2 but fails to filter based on "university.id" in v7.10.0.
The university and country are two different nested objects under the college document.
Any help would be appreciated!

Following it the query I'm using.

**Mapping**
PUT /college/_mapping/
{
    "properties": {
      "id": { "type": "keyword", "index": true},
      "collegeRank": { "type": "integer", "index": true},
      "university": {
        "type": "nested",
        "properties": {
            "id": { "type": "keyword", "index": true}
            
        }
      },
      "country": {
        "type": "nested",
        "properties": {
		      "fid": {"type": "keyword", "index": true}
        }
      }
    }
}
**Sample data**
 {
        "_index" : "college",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : null,
        "_source" : {
          "id" : "1",
          "collegeRank" : 18,
          "university" : {
            "id" : "100"
          },
          "country" : {
            "fid" : "USA"
          }
        },
        "sort" : [
          "1"
        ]
      },
      {
        "_index" : "college",
        "_type" : "_doc",
        "_id" : "2",
        "_score" : null,
        "_source" : {
          "id" : "2",
          "collegeRank" : 120,
          "university" : {
            "id" : "100"
          },
          "country" : {
            "fid" : "USA"
          }
        },
        "sort" : [
          "2"
        ]
      },
      {
        "_index" : "college",
        "_type" : "_doc",
        "_id" : "3",
        "_score" : null,
        "_source" : {
          "id" : "3",
          "collegeRank" : 300,
          "university" : {
            "id" : "200"
          },
          "country" : {
            "fid" : "GBR"
          }
        },
        "sort" : [
          "3"
        ]
      },
      {
        "_index" : "college",
        "_type" : "_doc",
        "_id" : "4",
        "_score" : null,
        "_source" : {
          "id" : "4",
          "collegeRank" : 150,
          "university" : {
            "id" : "200"
          },
          "country" : {
            "fid" : "DEU"
          }
        },
        "sort" : [
          "4"
        ]
      },
      {
        "_index" : "college",
        "_type" : "_doc",
        "_id" : "5",
        "_score" : null,
        "_source" : {
          "id" : "5",
          "collegeRank" : 2,
          "university" : {
            "id" : "200"
          },
          "country" : {
            "fid" : "DEU"
          }
        },
        "sort" : [
          "5"
        ]
      }
**Query**
GET college/_search
{
    "size": 0,
    "aggs" : {
        "byUniversity" : {
            "nested" : {
                "path" : "university"
            },
            "aggs" : {
                "byUniversityId" : {
                    "filter": {
                        "term": {
                            "university.id": "200"
                        }
                    },
                    "aggs": {
                        "byUniversityOrCollegeCountry" : {
                            "nested" : {
                                "path" : "country"
                            },
                            "aggs" : {
                                "byUniversityOrCollegeCountryId" : {
                                    "terms" : {
                                        "field" : "country.fid",
                                        "size" : 500
                                    },
                                    "aggs" : {
                                        "byCollege": {
                                            "reverse_nested": {},
                                            "aggs": {
                                                "topCollegeHit": {
                                                    "top_hits": {
                                                        "sort": [
                                                            {"collegeRank": {"order": "asc"}}
                                                        ],
                                                        "size": 1
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}
**Output on v5.3.2**

{
  "took": 3,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 5,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "byUniversity": {
      "doc_count": 5,
      "byUniversityId": {
        "doc_count": 3,
        "byUniversityOrCollegeCountry": {
          "doc_count": 3,
          "byUniversityOrCollegeCountryId": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
              {
                "key": "DEU",
                "doc_count": 2,
                "byCollege": {
                  "doc_count": 2,
                  "topCollegeHit": {
                    "hits": {
                      "total": 2,
                      "max_score": null,
                      "hits": [
                        {
                          "_index": "college",
                          "_type": "col",
                          "_id": "5",
                          "_score": null,
                          "_source": {
                            "id": "5",
                            "collegeRank": 2,
                            "university": {
                              "id": "200"
                            },
                            "country": {
                              "fid": "DEU"
                            }
                          },
                          "sort": [
                            2
                          ]
                        }
                      ]
                    }
                  }
                }
              },
              {
                "key": "GBR",
                "doc_count": 1,
                "byCollege": {
                  "doc_count": 1,
                  "topCollegeHit": {
                    "hits": {
                      "total": 1,
                      "max_score": null,
                      "hits": [
                        {
                          "_index": "college",
                          "_type": "col",
                          "_id": "3",
                          "_score": null,
                          "_source": {
                            "id": "3",
                            "collegeRank": 300,
                            "university": {
                              "id": "200"
                            },
                            "country": {
                              "fid": "GBR"
                            }
                          },
                          "sort": [
                            300
                          ]
                        }
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
}
**Output on v7.10.0**

{
  "took" : 4,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 5,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "byUniversity" : {
      "doc_count" : 5,
      "byUniversityId" : {
        "doc_count" : 3,
        "byUniversityOrCollegeCountry" : {
          "doc_count" : 1,
          "byUniversityOrCollegeCountryId" : {
            "doc_count_error_upper_bound" : 0,
            "sum_other_doc_count" : 0,
            "buckets" : [
              {
                "key" : "GBR",
                "doc_count" : 1,
                "byCollege" : {
                  "doc_count" : 1,
                  "topCollegeHit" : {
                    "hits" : {
                      "total" : {
                        "value" : 1,
                        "relation" : "eq"
                      },
                      "max_score" : null,
                      "hits" : [
                        {
                          "_index" : "college",
                          "_type" : "_doc",
                          "_id" : "3",
                          "_score" : null,
                          "_source" : {
                            "id" : "2",
                            "collegeRank" : 300,
                            "university" : {
                              "id" : "200"
                            },
                            "country" : {
                              "fid" : "GBR"
                            }
                          },
                          "sort" : [
                            300
                          ]
                        }
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
}

Can you share a full reproduction for the 7.10 example? Including index creation, some sample documents that re index and the query? This way it might help others to reproduce the problem.

Thank you!

Thanks for the suggestion, updated my post.