Problem with multi-sensor device MQTT configuration

I’ve been struggling with an mqtt configuration problem. I’m replacing an old alarm controller with a microcontroller based one. I’d like it to show in Home Assistant as a single device with multiple sensors, as shown in the image.

If I edit the configuration.yaml file with the following, it produces the above:

# Manually configured MQTT entities
mqtt:
  - binary_sensor:
    - name: EntryMotion
      device_class: motion
      state_topic: "home/EntryMotion"
      payload_on: 1
      payload_off: 0
      unique_id: mysensor1
      device:
        identifiers: HouseAlarm-ID
        name: HouseAlarm
    - name: RumpusMotion
      device_class: motion
      state_topic: "home/RumpusMotion"
      payload_on: 1
      payload_off: 0
      unique_id: mysensor2
      device:
        identifiers: HouseAlarm-ID
        name: HouseAlarm

However, coding this into mqtt discovery messages produces a device with one sensor and one orphaned sensor as a separate identity:

Topic: homeassistant/binary_sensor/EntryMotion/config

{ 
  "name": "EntryMotion",
  "device_class": "motion",
  "state_topic": "homeassistant/binary_sensor/EntryMotion/state",               
  "payload_on": 1,
  "payload_off": 0,
  "unique_id": "mysensor1",
  "device": {"identifiers": ["HouseAlarm-ID"], "name": "HouseAlarm"},                 
  "retain": true 
}

Topic: homeassistant/binary_sensor/RumpusMotion\config

{ 
  "name": "RumpusMotion",
  "device_class": "motion",
  "state_topic": "homeassistant/binary_sensor/RumpusMotion/state",  
  "payload_on": 1,
  "payload_off": 0,
  "unique_id": "mysensor2",
  "device": {"identifiers": ["HouseAlarm-ID"], "name": "HouseAlarm"},              
  "retain": true 
}

This isn’t my first try - I have multiple temperature / humidity sensors that work this way and they configure multiple sensors fine. It just seems to be the binary_sensor I’m having issues with.

Any help would be appreciated.
Thanks,
Phil