Unhashable type: 'NodeListClass'

Hi,
I have been using Home Assistant for a couple of years and can normally work out what I have got wrong in my configuration, but this one eludes me, so any help you can offer would be most welcome.

I have a Honeywell EvoHome thermostat and radiator valves, which has been working well for the whole time I have been using Home assistant. I decided that I would like to do some detailed logging of what is really going on with my central heating system, so every time there is a change of certain attributes of each radiator valve, I want to publish an MQTT message, which will be picked up by an MQTT logging app I have running elsewhere on my network.

I have the following automation:

##########################################################################
# Publish an MQTT message every time a Climate Zone's state changes
# The MQTT message will be used to report key Zone attributes
#
- alias: 'A Climate Zone has changed state'
  initial_state: true
  trigger: 
    platform: state
    entity_id: 
      - climate.backbedroom
      - climate.bathroom
      - climate.diningroom
      - climate.frontbedroom
      - climate.hallway
      - climate.kitchen
      - climate.landing
      - climate.lounge
      - climate.master
      - climate.towelrad
      - climate.utility
    attribute:
      - temperature
      - current_temperature
    to: 
  action:
  - service: mqtt.publish
    data_template: 
      topic: "Climate/"
      payload: "{{ state_attr(trigger.to_state.attributes.current_temperature) }},{{ state_attr(trigger.to_state.attributes.temperature) }}"
 

Whenever it fires, I receive the following error message in the log:

2022-01-01 16:48:22 ERROR (MainThread) [homeassistant.helpers.event] Error while processing state change for climate.backbedroom
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/event.py", line 269, in _async_state_change_dispatcher
    hass.async_run_hass_job(job, event)
  File "/usr/src/homeassistant/homeassistant/core.py", line 433, in async_run_hass_job
    hassjob.target(*args)
  File "/usr/src/homeassistant/homeassistant/components/homeassistant/triggers/state.py", line 122, in state_automation_listener
    old_value = from_s.attributes.get(attribute)
TypeError: unhashable type: 'NodeListClass'

I have no idea which part of of my automation is causing this problem, however as the error message occurs when it is fired, I presume it is somewhere in the action: section.

Thanks in advance

Sorry, forgot to state I am running supervisor-2021.12.2 and core-2021.12.7.