Zappi Fast mode not working in automation

Configuration
,
1

I’m trying to automate my setup to make best use of Octopus Power Up periods where electricity is free for a time.
I ma using calendar event start and end as my triggers to set it up and reset at the end which is working fine.
The problem is getting my zappi charger to charge my car.
When the event start triggers I set up

  1. My solar battery to charge and draw all power from the grid. That works fine.
  2. Turn off Octopus Intelligent Smart Charge .
  3. Check the zappi plug status is Connected.
  4. If Connected then set zappi Charge Mode to Fast.

It does everything, including setting charge mode to Fast but the charge mode reverts back to eco++ after a couple of minutes. I then have to set it manually via the myenergi app or zappi front panel.

Anyone know what I’m missing/where I’m going wrong?
Automation code below for reference.

alias: Octopus Power Up Start
description: >-
  Uses calendar event to swich on Battery first and EV Boost charge during
  Octopus Power Up
triggers:
  - trigger: calendar
    entity_id: calendar.octopus_power_ups
    event: start
    offset: "0:0:0"
conditions: []
actions:
  - action: switch.turn_off
    metadata: {}
    data: {}
    target:
      entity_id: switch.octopus_energy_a_********_intelligent_smart_charge
  - action: script.turn_on_growatt_battery_first
    metadata: {}
    data: {}
  - if:
      - condition: state
        entity_id: sensor.myenergi_zappi_********_plug_status
        state: EV Connected
    then:
      - action: select.select_option
        metadata: {}
        data:
          option: Fast
        target:
          entity_id: select.myenergi_zappi_********_charge_mode
mode: single