Tasmato Sonoff turns on/off after commanded by Alexa

I control the Tasmotas via Home Assistant with Mqtt. Also I have the Wemo Simulation enable to control them like this with my Alexa.

My Problem I have now, when I turn it on or off vie Alexa command, after a few minutes HA reverses the know state in HA back to the tasmota. So in Home Assistant it shows it is off aftzer I turned it on with Alexa. After a few minutes HA turn the device back off again.

I guess there is something wrong in my config about the state of the Tasmota:

switch:

  • platform: mqtt
    name: “Ventilator”
    command_topic: “cmnd/ventilator/POWER”
    state_topic: “stat/ventilator/POWER”
    qos: 1
    payload_on: “ON”
    payload_off: “OFF”
    payload_available: ‘online’
    payload_not_available: ‘offline’
    retain: true

Somebody can help me out with this?