When the local temperature of the TRV changes, update the calibration using an external temperature sensor.

sonoff_trvzb_calibration.yaml

blueprint:
    name: Sonoff TRVZB Calibration
    author: Niklas Vlach
    description: "
    
      When the local temperature of the TRV changes, update the calibration using an external temperature sensor.
      
      
      
      **Version**: 0.0.3
      
      "
    source_url: https://gist.github.com/NiklasZeroZero/80a5d880660b127b7fe461ebfac9ddf0
    domain: automation
    input:
        climate_entity:
            name: Climate Entity
            description: The climate entity published by the Sonoff TRVZB
            selector:
                entity:
                    filter:
                    - domain: climate
                    multiple: false
        local_temperature_calibration_entity:
            name: Local Temperature Calibration Entity
            description: The temperature calibration entity published by the Sonoff TRVZB
            selector:
                entity:
                    filter:
                    - domain: number
                    multiple: false
        temperature_sensor_entity:
            name: Temperature Sensor Entity
            description: The external room temperature sensor entity.
            selector:
                entity:
                    filter:
                    - domain: sensor
                    multiple: false
mode: single
max_exceeded: silent
trigger:
  - platform: state
    entity_id:
      - !input climate_entity
    attribute: current_temperature
condition:
  - condition: or
    conditions:
      - condition: numeric_state
        entity_id: !input climate_entity
        attribute: current_temperature
        above: !input temperature_sensor_entity
      - condition: numeric_state
        entity_id: !input climate_entity
        attribute: current_temperature
        below: !input temperature_sensor_entity
action:
  - variables:
      climate_entity: !input climate_entity
      local_temperature_calibration_entity: !input local_temperature_calibration_entity
      temperature_sensor_entity: !input temperature_sensor_entity
      trvtemp: "{{ state_attr(climate_entity, 'current_temperature') }}"
      trvcalib: "{{ states(local_temperature_calibration_entity) }}"
      roomtemp: "{{ states(temperature_sensor_entity) }}"
      calibration: "{{ ([-7, (trvcalib - (trvtemp - roomtemp)) | float | round(2), 7] | sort)[1] }}"
  - action: number.set_value
    target:
      entity_id: !input local_temperature_calibration_entity
    data:
      value: "{{calibration}}"

Excuse me, there was a similar script generated by ChatGPT, which was triggered after HA was restarted.

The only log entry related to your script is:
error: zhc: Failed to apply calibration to 'device_temperature': 'device_temperature_calibration' is not a number, got string ()