os documentos não vão para o fragmento recém-adicionado

Adicionei um shard a um cluster existente e, quando faço db.printShardingStatus(), vejo uma distribuição:

mongos> db.printShardingStatus()
--- Sharding Status --- 
  sharding version: {
    "_id" : 1,
    "minCompatibleVersion" : 5,
    "currentVersion" : 6,
    "clusterId" : ObjectId("5c84149e75f51a74e9796add")
  }
  shards:
        {  "_id" : "shard0000",  "host" : "127.0.0.1:27023",  "state" : 1 }
        {  "_id" : "shard0001",  "host" : "127.0.0.1:27024",  "state" : 1 }
        {  "_id" : "shard0002",  "host" : "localhost:27025",  "state" : 1 }
  active mongoses:
        "4.0.6" : 1
  autosplit:
        Currently enabled: yes
  balancer:
        Currently enabled:  yes
        Currently running:  no
        Failed balancer rounds in last 5 attempts:  3
        Last reported error:  Error connecting to localhost:27025 (127.0.0.1:27025) :: caused by :: Connection refused
        Time of Reported error:  Sat Mar 09 2019 20:55:55 GMT+0000 (UTC)
        Migration Results for the last 24 hours: 
                8 : Success
  databases:
        {  "_id" : "config",  "primary" : "config",  "partitioned" : true }
                config.system.sessions
                        shard key: { "_id" : 1 }
                        unique: false
                        balancing: true
                        chunks:
                                shard0000   1
                        { "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0000 Timestamp(1, 0) 
        {  "_id" : "testdb",  "primary" : "shard0001",  "partitioned" : true,  "version" : {  "uuid" : UUID("68b7f8fe-17f6-4049-87ce-6c616c7746b7"),  "lastMod" : 1 } }
                testdb.testcollection
                        shard key: { "testkey" : 1 }
                        unique: false
                        balancing: true
                        chunks:
                                shard0000   3
                                shard0001   3
                                shard0002   1
                        { "testkey" : { "$minKey" : 1 } } -->> { "testkey" : "key0" } on : shard0002 Timestamp(9, 0) 
                        { "testkey" : "key0" } -->> { "testkey" : "key20968" } on : shard0000 Timestamp(7, 1) 
                        { "testkey" : "key20968" } -->> { "testkey" : "key4265" } on : shard0000 Timestamp(4, 0) 
                        { "testkey" : "key4265" } -->> { "testkey" : "key53621" } on : shard0000 Timestamp(6, 0) 
                        { "testkey" : "key53621" } -->> { "testkey" : "key64595" } on : shard0001 Timestamp(5, 1) 
                        { "testkey" : "key64595" } -->> { "testkey" : "key8552" } on : shard0001 Timestamp(9, 1) 
                        { "testkey" : "key8552" } -->> { "testkey" : { "$maxKey" : 1 } } on : shard0001 Timestamp(4, 1) 

Mas quando eu acesso o shard recém adicionado (shard0002), a coleção está vazia? Alguem sabe por quê?