_reindex in "Dev Tools" OSD 2.7 not working as expected

I have two clusters:
PROM: version OpenSearch + OpensearchDashboards 2.3.0
TEST: version OpenSearch + OpensearchDashboards 2.7.0 (updated from 2.3.0, PROM mirror)

cluster settings are the same
I do the same actions with the same index in “Dev Tools”:

POST _reindex
{
  "source": {
    "index": "elk_12-test-1"
  },
  "dest": {
    "index": "elk_12-test-2"
  }
}
On PROM I see one task
GET /_tasks?detailed=true&actions=*reindex*

{
  "nodes" : {
    "uwuvGpUfSOOTLKVVMBB_0Q" : {
      "name" : "node_name",
      "transport_address" : "xxx.xxx.xxx.xxx:9300",
      "host" : "xxx.xxx.xxx.xxx",
      "ip" : "xxx.xxx.xxx.xxx:9300",
      "roles" : [
        "ingest",
        "remote_cluster_client"
      ],
      "attributes" : {
        "zone" : "vlg",
        "shard_indexing_pressure_enabled" : "true"
      },
      "tasks" : {
        "uwuvGpUfSOOTLKVVMBB_0Q:256784238" : {
          "node" : "uwuvGpUfSOOTLKVVMBB_0Q",
          "id" : 256784238,
          "type" : "transport",
          "action" : "indices:data/write/reindex",
          "status" : {
            "total" : 4131710,
            "updated" : 0,
            "created" : 2703000,
            "deleted" : 0,
            "batches" : 2704,
            "version_conflicts" : 0,
            "noops" : 0,
            "retries" : {
              "bulk" : 0,
              "search" : 0
            },
            "throttled_millis" : 0,
            "requests_per_second" : -1.0,
            "throttled_until_millis" : 0
          },
          "description" : "reindex from [elk_12-test-1] to [elk_12-test-2]",
          "start_time_in_millis" : 1684114612633,
          "running_time_in_nanos" : 1263598777066,
          "cancellable" : true,
          "cancelled" : false,
          "headers" : { },
          "resource_stats" : {
            "total" : {
              "cpu_time_in_nanos" : 0,
              "memory_in_bytes" : 0
            }
          }
        }
      }
    }
  }
}

When the task completed i see two identical indices

GET _cat/indices/elk_12-test-*?v&s=index 

health status index         uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   elk_12-test-1 gm8j0speTg2eDlyszyoPGQ   1   1    4131710            0      3.3gb          1.7gb
green  open   elk_12-test-2 oRlt73zDQzGmbImHR8HxyA   1   1    4131710            0      3.3gb          1.7gb
In TEST, the same actions lead to the creation of four tasks
GET /_tasks?detailed=true&actions=*reindex*
{
  "nodes": {
    "JIy8hrGuSoWNE5KDeNCBnQ": {
      "name": "vlg-node_name",
      "transport_address": "xxx.xxx.xxx.xx1:9300",
      "host": "xxx.xxx.xxx.xx1",
      "ip": "xxx.xxx.xxx.xx1:9300",
      "roles": [
        "cluster_manager",
        "data"
      ],
      "attributes": {
        "type": "hist",
        "zone": "vlg",
        "shard_indexing_pressure_enabled": "true"
      },
      "tasks": {
        "JIy8hrGuSoWNE5KDeNCBnQ:47392246": {
          "node": "JIy8hrGuSoWNE5KDeNCBnQ",
          "id": 47392246,
          "type": "transport",
          "action": "indices:data/write/reindex",
          "status": {
            "total": 4131710,
            "updated": 192000,
            "created": 711000,
            "deleted": 0,
            "batches": 904,
            "version_conflicts": 0,
            "noops": 0,
            "retries": {
              "bulk": 0,
              "search": 0
            },
            "throttled_millis": 0,
            "requests_per_second": -1,
            "throttled_until_millis": 0
          },
          "description": "reindex from [elk_12-test-1] to [elk_12-test-2]",
          "start_time_in_millis": 1684120039895,
          "running_time_in_nanos": 250233204932,
          "cancellable": true,
          "cancelled": false,
          "headers": {
            "X-Opaque-Id": "bb70ea0c-6423-4d67-a04b-d0cccbe2d9f4"
          },
          "resource_stats": {
            "total": {
              "cpu_time_in_nanos": 0,
              "memory_in_bytes": 0
            }
          }
        },
        "JIy8hrGuSoWNE5KDeNCBnQ:47394749": {
          "node": "JIy8hrGuSoWNE5KDeNCBnQ",
          "id": 47394749,
          "type": "transport",
          "action": "indices:data/write/reindex",
          "status": {
            "total": 4131710,
            "updated": 706000,
            "created": 0,
            "deleted": 0,
            "batches": 707,
            "version_conflicts": 0,
            "noops": 0,
            "retries": {
              "bulk": 0,
              "search": 0
            },
            "throttled_millis": 0,
            "requests_per_second": -1,
            "throttled_until_millis": 0
          },
          "description": "reindex from [elk_12-test-1] to [elk_12-test-2]",
          "start_time_in_millis": 1684120099897,
          "running_time_in_nanos": 190231243720,
          "cancellable": true,
          "cancelled": false,
          "headers": {
            "X-Opaque-Id": "bb70ea0c-6423-4d67-a04b-d0cccbe2d9f4"
          },
          "resource_stats": {
            "total": {
              "cpu_time_in_nanos": 0,
              "memory_in_bytes": 0
            }
          }
        }
      }
    },
    "teEcyYF5RkOkLI-3O1kLPA": {
      "name": "kvk-node_name",
      "transport_address": "xxx.xxx.xxx.xx2:9300",
      "host": "xxx.xxx.xxx.xx2",
      "ip": "xxx.xxx.xxx.xx2:9300",
      "roles": [
        "cluster_manager",
        "data"
      ],
      "attributes": {
        "zone": "kvk",
        "shard_indexing_pressure_enabled": "true",
        "type": "hist"
      },
      "tasks": {
        "teEcyYF5RkOkLI-3O1kLPA:62329456": {
          "node": "teEcyYF5RkOkLI-3O1kLPA",
          "id": 62329456,
          "type": "transport",
          "action": "indices:data/write/reindex",
          "status": {
            "total": 4131710,
            "updated": 248000,
            "created": 0,
            "deleted": 0,
            "batches": 249,
            "version_conflicts": 0,
            "noops": 0,
            "retries": {
              "bulk": 0,
              "search": 0
            },
            "throttled_millis": 0,
            "requests_per_second": -1,
            "throttled_until_millis": 0
          },
          "description": "reindex from [elk_12-test-1] to [elk_12-test-2]",
          "start_time_in_millis": 1684120159884,
          "running_time_in_nanos": 130226594041,
          "cancellable": true,
          "cancelled": false,
          "headers": {
            "X-Opaque-Id": "bb70ea0c-6423-4d67-a04b-d0cccbe2d9f4"
          },
          "resource_stats": {
            "total": {
              "cpu_time_in_nanos": 0,
              "memory_in_bytes": 0
            }
          }
        },
        "teEcyYF5RkOkLI-3O1kLPA:62318811": {
          "node": "teEcyYF5RkOkLI-3O1kLPA",
          "id": 62318811,
          "type": "transport",
          "action": "indices:data/write/reindex",
          "status": {
            "total": 4131710,
            "updated": 385000,
            "created": 192000,
            "deleted": 0,
            "batches": 578,
            "version_conflicts": 0,
            "noops": 0,
            "retries": {
              "bulk": 0,
              "search": 0
            },
            "throttled_millis": 0,
            "requests_per_second": -1,
            "throttled_until_millis": 0
          },
          "description": "reindex from [elk_12-test-1] to [elk_12-test-2]",
          "start_time_in_millis": 1684119979799,
          "running_time_in_nanos": 310311123109,
          "cancellable": true,
          "cancelled": false,
          "headers": {
            "X-Opaque-Id": "bb70ea0c-6423-4d67-a04b-d0cccbe2d9f4"
          },
          "resource_stats": {
            "total": {
              "cpu_time_in_nanos": 0,
              "memory_in_bytes": 0
            }
          }
        }
      }
    }
  }
}

This causes a lot of updates, which I then see as deleted documents

GET _cat/indices/elk_12-test-*?v&s=index 

health status index         uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   elk_12-test-1 BKdnoMW-SwmWvNm9O991QA   1   1    4131710            0      2.3gb          1.1gb
green  open   elk_12-test-2 A1wCcTqMRr-IpRlPO0gUGQ   1   1    4131710      1503420        3gb          1.6gb

If I execute a query through the API, then this behavior is not observed, the index is created without “garbage” and much faster in time

Summary
request:
curl -XPOST -u username -H 'Content-Type: application/json' 'https://vlg-node_name:9200/_reindex' -d '{ "source": { "index": "elk_12-test-1"}, "dest": { "index": "elk_12-test-3" } }'
{"took":1920489,"timed_out":false,"total":4131710,"updated":0,"created":4131710,"deleted":0,"batches":4132,"version_conflicts":0,"noops":0,"retries":{"bulk":0,"search":0},"throttled_millis":0,"requests_per_second":-1.0,"throttled_until_millis":0,"failures":[]}


One task:
GET /_tasks?detailed=true&actions=*reindex*
{
  "nodes": {
    "JIy8hrGuSoWNE5KDeNCBnQ": {
      "name": "vlg-node_name",
      "transport_address": "xxx.xxx.xxx.xx1:9300",
      "host": "xxx.xxx.xxx.xx1",
      "ip": "xxx.xxx.xxx.xx1:9300",
      "roles": [
        "cluster_manager",
        "data"
      ],
      "attributes": {
        "type": "hist",
        "zone": "vlg",
        "shard_indexing_pressure_enabled": "true"
      },
      "tasks": {
        "JIy8hrGuSoWNE5KDeNCBnQ:47463338": {
          "node": "JIy8hrGuSoWNE5KDeNCBnQ",
          "id": 47463338,
          "type": "transport",
          "action": "indices:data/write/reindex",
          "status": {
            "total": 4131710,
            "updated": 0,
            "created": 454000,
            "deleted": 0,
            "batches": 455,
            "version_conflicts": 0,
            "noops": 0,
            "retries": {
              "bulk": 0,
              "search": 0
            },
            "throttled_millis": 0,
            "requests_per_second": -1,
            "throttled_until_millis": 0
          },
          "description": "reindex from [elk_12-test-1] to [elk_12-test-3]",
          "start_time_in_millis": 1684121585862,
          "running_time_in_nanos": 208521588983,
          "cancellable": true,
          "cancelled": false,
          "headers": {},
          "resource_stats": {
            "total": {
              "cpu_time_in_nanos": 0,
              "memory_in_bytes": 0
            }
          }
        }
      }
    }
  }
}

Indices:
GET _cat/indices/elk_12-test-*?v&s=index 
green  open   elk_12-test-1 BKdnoMW-SwmWvNm9O991QA   1   1    4131710            0      2.3gb          1.1gb
green  open   elk_12-test-2 A1wCcTqMRr-IpRlPO0gUGQ   1   1    4131710      1503420        3gb          1.6gb
green  open   elk_12-test-3 iVsgJ_G4Tn6NPAanUPL8hw   1   1    4131710            0      2.3gb          1.1gb

Looks like OpensearchDashboards 2.7 is sending multiple requests. In the old version, this behavior was not observed.