WARNING (MainThread) [homeassistant.components.mqtt.cover] Payload 'None' is not numeric

Configuration
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1

Hi, I got the problem that my HA host frequently dies. (not reachable via network, have to reboot it)
When looking into the journal I find those lines:
WARNING (MainThread) [homeassistant.components.mqtt.cover] Payload ‘None’ is not numeric

massively.

Sometimes, the computer is still reachable (also is HA) but directly after shutting the covers, some go up again randomly

I use tasmota based shutter controllers: https://currysmarter.com/product/tasmota-rollladenschalter/

maybe I do something wrong?
Followed the descriptions I found here (will post them when I find them again) and my result looks like this:

mqtt:
  cover:
    - name: "yamlShutter"
      unique_id: "yamlShutterId"
      qos: 1
      command_topic: "cmnd/Rolladen_WZ/tuyasend4"
      payload_open: "1,0"
      payload_close: "1,2"
      payload_stop: "1,1"
      set_position_topic: "cmnd/Rolladen_WZ/shutterposition"
      set_position_template: "{{value}}"
      position_topic: "stat/Rolladen_WZ/RESULT"
      position_template: >
        {% if ('Shutter1' in value_json) and ('Position' in value_json.Shutter1) %}
          {{ value_json.Shutter1.Position }}
        {% else %}
          {% if is_state('cover.balcony_blinds', 'unknown') %}
            50
          {% else %}
            {{ state_attr('cover.balcony_blinds','current_position') }}
          {% endif %}
        {% endif %} 
      availability_topic: "tele/Rolladen_WZ/LWT"
      payload_available: "Online"
      payload_not_available: "Offline"

Maybe someone can tell me whats wrong here?