Shelly3EM with 'statistics' platform - evaluating single phase power changes

Hi,
based on an idea by Klaus Urban on Facebook (Home Assistant Tipps und Tricks | Facebook) , I wanted to get a notification for the total power change or the power change of only one phase. The automation can be activated by a boolean input variable in my frontend.

For ‘total power’ it works fine, but as soon as I do add some single phase measurements, the final statistics variable remains ‘unavailable’.

My configuration. yaml includes

sensor:
  - platform: statistics
    name: "Verbrauchsanderung"
    entity_id: sensor.power_total
    state_characteristic: change
    max_age:
      seconds: 15
      
  - platform: statistics    
    name: "Verbrauchsanderung_Phase1"
    entity_id: sensor.power_phase1
    state_characteristic: change
    max_age:
      seconds: 15
      
  - platform: statistics
    name: "Verbrauchsanderung_Phase2"
    entity_id: sensor.power_phase2
    state_characteristic: change
    max_age:
      seconds: 15
      
  - platform: statistics
    name: "Verbrauchsanderung_Phase3"
    entity_id: sensor.power_phase3
    state_characteristic: change
    max_age:
      seconds: 15  

my ‘template.yaml’ includes:

  - sensor:
    - name: "Energy Total"
      unique_id: energy_total
      state: >-
        {{ states('sensor.shellyem3_e89f6d852b3a_channel_a_energy')|float + 
           states('sensor.shellyem3_e89f6d852b3a_channel_b_energy')|float + 
           states('sensor.shellyem3_e89f6d852b3a_channel_c_energy')|float }}
      unit_of_measurement: kWh
      device_class: energy
      state_class: total_increasing
      attributes:
        last_reset: "1970-01-01T00:00:00+00:00"
      availability: >
       {{ not 'unavailable' in 
          [ states('sensor.shellyem3_e89f6d852b3a_channel_a_energy'), 
            states('sensor.shellyem3_e89f6d852b3a_channel_b_energy'),
            states('sensor.shellyem3_e89f6d852b3a_channel_c_energy') ] }} 
    - name: "Power Total"
      unique_id: power_total
      state: >-
        {{ states('sensor.shellyem3_e89f6d852b3a_channel_a_power')|float + states('sensor.shellyem3_e89f6d852b3a_channel_b_power')|float + states('sensor.shellyem3_e89f6d852b3a_channel_c_power')|float }}
      unit_of_measurement: W
      device_class: power
      state_class: measurement
    - name: "Power Phase 1"
      unique_id: power_phase1
      state:  >-
        {{ states('sensor.shellyem3_e89f6d852b3a_channel_a_power')|float }}
      unit_of_measurement: W
      device_class: power
      state_class: measurement
    - name: "Power Phase 2"
      unique_id: power_phase2
      state: >-
        {{ states('sensor.shellyem3_e89f6d852b3a_channel_b_power')|float }}
      unit_of_measurement: W
      device_class: power
      state_class: measurement
    - name: "Power Phase 3"
      unique_id: power_phase3
      state: >-
        {{ states('sensor.shellyem3_e89f6d852b3a_channel_c_power')|float }}
      unit_of_measurement: W
      device_class: power
      state_class: measurement

Any ideas?
I did copy the source code identical to the total power…

Regards
Joerg