Intent_script + snips: unable to change tv channel

Configuration
1

Hello,
I’m trying to change tv channel with my voice across snips.

My configuration.yaml

intent_script:
  tvChangeChannel:
    action:
      - service: media_player.play_media
        data:
          entity_id: media_player.lg_webos_smart_tv
          media_content_type: "channel"
        data_template:
          media_content_id: "{{tv_channel}}"

My snips assistant intent:

intents" : [ {
    "id" : "adrianofoschi:tvChangeChannel",
    "type" : "registry",
    "version" : "0.6.0",
    "language" : "it",
    "slots" : [ {
      "name" : "tv_channel",
      "id" : "5K2xOzcwt",
      "entityId" : "snips/number",
      "missingQuestion" : "",
      "required" : false
    } ],
    "name" : "tvChangeChannel",
    "enabledByDefault" : true
  }

And snips-watch output of my voice

[18:15:18] [Nlu] detected intent adriano:tvChangeChannel with confidence score 0.681 for input "avvia canale uno"
              Slots ->
                 tv_channel -> 1 (confidence: 1.000) 
[18:15:18] [Dialogue] New intent detected adrianofoschi:tvChangeChannel with confidence 0.681
              Slots ->
                 tv_channel -> 1 (confidence: 1.000)

It doesn’t work.
It works if I replace “{{tv_channel}}” with a number, 5 for example.