ESPHome Modbus Server write register

I have made a Modbus MitM module for my Growatt Inverter.
Reading values from the inverter and presenting them to another Modbus Client (Master) works fine.
Also setting values with the MitM module on the Inverter works fine.
However changing settings on the Modbus Client and write them to the MitM module does not work.

Part of the code I use is the following:

preferences:
  flash_write_interval: 1h

uart:
  - id: mod_bus
    tx_pin: 19
    rx_pin: 18
    baud_rate: 9600
  - id: uart_modbus_server
    tx_pin: 16
    rx_pin: 17
    baud_rate: 9600

modbus:
  - uart_id: mod_bus
    id: modbus1
  - uart_id: uart_modbus_server
    id: modbus_server
    role: server

modbus_controller:
  - id: growatt
    address: 0x1
    update_interval: 10s
    modbus_id: modbus1
    setup_priority: -10  
  - id: growatt_server
    modbus_id: modbus_server
    address: 0x1
    server_registers:
      - address: 0
        value_type: U_WORD
        read_lambda: |-
          return id(inverter).state;
      - address: 122
        value_type: U_WORD
        read_lambda: |-
          return id(antibackflow).state;
      - address: 123
        value_type: S_WORD
        read_lambda: |-
          return id(antibackflowrate).state;            

number:
  - platform: modbus_controller
    modbus_controller_id: growatt  
    id: antibackflowrate
    name: "Antibackflow Rate"
    address: 123
    register_type: holding
    value_type: S_WORD
    min_value: -1000
    max_value: 1000
    step: 10


sensor:    
  - platform: wifi_signal
    name: "WiFi Signal Sensor"
    update_interval: 60s

  - platform: modbus_controller
    modbus_controller_id: growatt  
    id: inverter
    internal: true
    name: "Inverter"
    icon: mdi:battery-charging-100
    address: 00
    register_type: "read"
    value_type: U_WORD

  - platform: modbus_controller
    modbus_controller_id: growatt
    id: runtime
    internal: true
    name: "Runtime"
    address: 57
    register_type: "read"
    value_type: U_DWORD
    on_value:
      then:
        - sensor.template.publish:
            id: runtime2
            state: !lambda |-
              return x * 0.5;

  - platform: modbus_controller
    modbus_controller_id: growatt  
    name: "AntiBackflow"
    internal: true
    address: 122
    register_type: holding   
    id: antibackflow

Error message on the Modbus client (Master) with MitM module connected and write command issued:

[21:55:56][D][modbus_controller:037]: Modbus command to device=1 register=0x00 countdown=0 no response received - removed from send queue
The MitM module seems to receive the following data at that moment:

[D][uart_debug:114]: <<< 010060000000000000890CA

What am I doing wrong? Is there a way to have a Modbus Client write values to a ESPHome Modbus Server?

any updates about the progress ?