Manually configured entities (via configuration.yaml) not loading after update

I had a setup that was showing me data on the dashboard via 2 sensor entities that were manually configured in configuration.yaml. The data from the ‘sensors’ came in via MQTT mosquitto.
Since the december update, my entities went missing

The configuration is as follow (extract from configuration.yaml with passwords and keys blanked ou) :

  username: MQTTHome
  password: *****
  client_id: home-assistant

sensor 2:
  - name: 'Warmwater'
    platform: mqtt
    state_topic: 'Badkamer/Warmwater'
    unit_of_measurement: °C
sensor 3:
  - name: 'Helderheid'
    platform: mqtt
    state_topic: 'Badkamer/Helderheid'
    unit_of_measurement: lx
sensor 1:
  - platform: emoncms
    api_key: *******
    id: 1

What might be wrong here?

the configuration of MQTT sensors has changed:

By the way, keep an eye on release notes, this has been announced for last couple of months