Running MirrorMaker in a Connect cluster,but the task not running

when i am Running MirrorMaker in a Connect clusterwhen i am Running MirrorMaker in a Connect cluster，sometime the task running，but sometime the task cannot assignment。
I post connector config to connect cluster，here is my config
http://99.12.98.33:8083/connectorshttp://99.12.98.33:8083/connectors
{    "name": "kafka->kafka241-3",   

"config":

{            "connector.class": "org.apache.kafka.connect.mirror.MirrorSourceConnector",          "topics": "MM2-3",          "key.converter": "org.apache.kafka.connect.converters.ByteArrayConverter",                       "value.converter": "org.apache.kafka.connect.converters.ByteArrayConverter",      "tasks.max": 8,      "sasl.mechanism": "PLAIN",     "security.protocol": "SASL_PLAINTEXT",     "sasl.jaas.config": "org.apache.kafka.common.security.plain.PlainLoginModule required username=\"admin\" password=\"admin\";",           "source.cluster.alias": "kafka",     "source.cluster.bootstrap.servers": "55.13.104.70:9092,55.13.104.74:9092,55.13.104.126:9092",      "source.admin.sasl.mechanism": "PLAIN",      "source.admin.security.protocol": "SASL_PLAINTEXT",      "source.admin.sasl.jaas.config": "org.apache.kafka.common.security.plain.PlainLoginModule required username=\"admin\" password=\"admin\";",          "target.cluster.alias": "kafka241",     "target.cluster.bootstrap.servers": "55.14.111.22:9092,55.14.111.23:9092,55.14.111.25:9092",     "target.admin.sasl.mechanism": "PLAIN",      "target.admin.security.protocol": "SASL_PLAINTEXT",    "target.admin.sasl.jaas.config": "org.apache.kafka.common.security.plain.PlainLoginModule required username=\"admin\" password=\"admin\";",         "producer.sasl.mechanism": "PLAIN",     "producer.security.protocol": "SASL_PLAINTEXT",      "producer.sasl.jaas.config": "org.apache.kafka.common.security.plain.PlainLoginModule required username=\"admin\" password=\"admin\";",           "consumer.sasl.mechanism": "PLAIN",     "consumer.security.protocol": "SASL_PLAINTEXT",     "consumer.sasl.jaas.config": "org.apache.kafka.common.security.plain.PlainLoginModule required username=\"admin\" password=\"admin\";",      "consumer.group.id": "mm2-1"        }

}

 

but I get the connector status，found not tasks running

http://99.12.98.33:8083/connectors/kafka->kafka241-3/status

{
"name": "kafka->kafka241-3",
"connector":

{ "state": "RUNNING", "worker_id": "99.12.98.34:8083" }

,
"tasks": [],
"type": "source"
}

 

but sometime，the task run success

http://99.12.98.33:8083/connectors/kafka->kafka241-1/status
{
"name": "kafka->kafka241-1",
"connector":

{ "state": "RUNNING", "worker_id": "99.12.98.34:8083" }

,
"tasks": [

{ "id": 0, "state": "RUNNING", "worker_id": "99.12.98.34:8083" }

,

{ "id": 1, "state": "RUNNING", "worker_id": "99.12.98.33:8083" }

,

{ "id": 2, "state": "RUNNING", "worker_id": "99.12.98.34:8083" }

],
"type": "source"
}

is somebody met this problem？ how to fix it，is it a bug？