Telegraf - MQTT Consumer (String values)

Hello,
I am using influxDB 2, cloud edition and I am ingesting my data using telegraf and the MQTT consumer.
With the float and int values it work fine, however telegraf refuse pushing the string values and I have no error from the debug mode.

This is my mqtt message:
{ “timestamp”: “05/05/2019 15:45”, " gps_coordinate “: " 49.5011866,0.1140913”} // not detected by telegraf
{ “timestamp”: “05/05/2019 15:45”, " altitude": 58 } // detected by telegraf
{ “timestamp”: “05/05/2019 15:45”, " orientation": 0 } // detected by telegraf
{ “timestamp”: “05/05/2019 15:45”, " speed": 0} // detected by telegraf

and this is my Telegraf.conf file:

Configuration for telegraf agent

[agent]

interval = “10s”
round_interval = true
metric_batch_size = 1000
metric_buffer_limit = 10000
collection_jitter = “0s”
flush_interval = “10s”
flush_jitter = “0s”
debug = true
omit_hostname = true

[[outputs.influxdb_v2]]

urls = [“https://xxxxxxxxx.aws.cloud2.influxdata.com”]
token = “xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx==”
organization = “xxxxxxxxxxx@xxx.com
bucket = “xxxx_bucket”

[[inputs.mqtt_consumer]]
servers = [“ssl://xxxxxxxxxxxxxxxx-ats.iot.us-west-2.amazonaws.com:8883”]
topics = [
“EP01”,
]
topic_tag = “Tender”
qos = 1
persistent_session = true
client_id = “telegraf_client”
tls_ca = “amazonrootca1.pem”
tls_cert = “thing-certificate.pem.crt”
tls_key = “private.pem.key”
data_format = “json”
json_time_key = “timestamp”
json_time_format = “02/01/2006 15:04”
json_timezone = “Local”

Can you try adding json_string_fields = [" gps_coordinate “] to your inputs.mqtt_consumer and see if that works?