False trigger when sensor becomes unavailable

Configuration
16

Thanks for the suggestion amelchio but for now the history stats sensor has solved the problem and I have no more false triggers. Until it is fixed with an official HA update here’s my code in case it helps anyone else:
within the sensor section of config yaml:

  - platform: history_stats
    name: PM1 Available
    entity_id: switch.pm1_switch
    state: "unavailable"
    type: time
    duration: 00:02:30
    end: "{{ now() }}"

and added as a condition with the automation:

  condition:
  - condition: numeric_state
    entity_id: sensor.pm1_available
    below: '0.01'

The template condition is probably a neater way to solve it but I know this works so for now I will leave well alone.