Sonoff CH4 with Tasmota does not switch off with timer

I have installed two Sonoff CH4 Pro devices with Tasmota for my irrigation system. I have integrated them into Home Assistant via MQTT. I can turn the individual relays on and off using the dashboard. However, I want to control the duration of an irrigation sequence using a timer. For this purpose, I have placed a timer on the dashboard. An automation is supposed to automatically switch off the irrigation after the set time. Unfortunately, the automatic shut-off is not working.
My entity in YAML:

    - name: "Bewässerung Rasen vorne"
      unique_id: sonoff_bewaesserung_1
      command_topic: "cmnd/tasmota_E2C7C2/POWER1"
      state_topic: "stat/tasmota_E2C7C2/POWER1"
      payload_on: "ON"
      payload_off: "OFF"
      state_on: "ON"
      state_off: "OFF"
      qos: 1
      retain: false

my automation:

- id: '1743298765001'
  alias: Bewässerung automatisch ausschalten nach Timer
  description: Schaltet das Bewässerungsrelais nach x Minuten aus, basierend auf dem aktuellen Timerwert
  mode: parallel
  trigger:
    - platform: state
      entity_id:
        - switch.sonoff_bewaesserung_1
        - switch.sonoff_bewaesserung_2
        - switch.sonoff_bewaesserung_3
        - switch.sonoff_bewaesserung_4
        - switch.sonoff_bw2_relais_1
        - switch.sonoff_bw2_relais_2
        - switch.sonoff_bw2_relais_3
        - switch.sonoff_bw2_relais_4
      to: 'on'
  condition:
    - condition: template
      value_template: >
        {{ states('input_number.timer_bewasserung') not in ['unknown', 'unavailable', '' ] }}
  action:
    - variables:
        ziel_relais: '{{ trigger.entity_id }}'
        dauer: '{{ states("input_number.timer_bewasserung") | int }}'
    - service: system_log.write
      data:
        message: "Starte Bewässerung an {{ ziel_relais }} für {{ dauer }} Minuten"
        level: info
    - delay:
        minutes: "{{ states('input_number.timer_bewasserung') | int }}"
    - service: switch.turn_off
      target:
        entity_id: '{{ ziel_relais }}'

I can’t figure out why the “unique_id: sonoff_bewaesserung_1” is not switching off automatically. Can you help me?