Automation wont execute (because of variable?)

using

  - alias: Frost sets shutters
    id: frost_sets_shutters
    variables:
      shutters: >
        {{states.cover
          |rejectattr('entity_id','search','template|homekit|low')
          |selectattr('entity_id','search','rolluik')
          |selectattr('attributes.current_position','defined')
          |selectattr('attributes.current_position','<=', 15)
          |map(attribute='entity_id')
          |list}}
    trigger:
      platform: numeric_state
      entity_id: sensor.buienradar_temperature
      below: -2
    condition:
      - >
        {{shutters|length > 0}}
    action:
      service: cover.set_cover_position
      target:
        entity_id: >
          {{shutters|join(', ')}}
      data:
        position: >
          {{'15' if 13 > states('sensor.buienradar_temperature')|float(0) < -1 else '0'}}

seems to be valid but nonetheless results in:

and the execution tree is even more mysterious, mentioning the entity-d’s twice:

could anyone please check what is wrong here?
thx for any thoughts you might have

guess I made a mistake in the position template, whihc would under the current conditions always be 0, so No motion was caused…

also, I forgot to set a <= 15 so if the covers were at 15, the list would be empty…

lets see what will happen this freezing night…