Help with mini-media-player shortcuts

Hi All,

I am trying to get some shortcut buttons created for the mini-media-player card. Specifically I want the buttons to change the source of the receiver to which this card points. I realize there is a dropdown for Source but I am hoping to get this to work instead.

type: custom:mini-media-player
name: Basement TV
entity: media_player.basement_receiver
toggle_power: true
volume_stateless: true
artwork: material
source: full
icon: mdi:television
sound_mode: full
info: scroll
max_volume: '100'
min_volume: '1'
  columns: 4
    - icon: mdi:television
      name: TV
      service: media_player.select_source
        source: TV

I keep getting the following error:

Failed to call service media_player/play_media. required key not provided @ data['media_content_type']

I have tried adding the entity ID into the data block as well as changing the data block to be servic_data.

If I add media_content_type: video, still no dice.

Anyone have any ideas what I am doing wrong here?