Modbus sometimes unreliable after restart / wrong configuration

I have the following problem. I have been switching my ventilation system via Modbus from my HA for a few years. It worked absolutely reliably until last year.

If HA now e.g. must be restarted by an update, switches and entities are always available for 20 seconds and then unavailable for 20 seconds. This keeps repeating itself!! This is not how my automation works reliably. If I then restart HA 1-40 times, there will eventually be a state where everything works permanently, completely without failure! So long until I have to start again and then get annoyed again. I’m actually very sure that I did something wrong in the configuration … I think I tried everything there without success, so I’m hoping for help here.


  - name: KomfoventRLT
    close_comm_on_error: false
    retry_on_empty: true
    retries: 10
    delay: 10
    message_wait_milliseconds: 1000
    timeout: 10
    type: tcp
    port: 502
      - name: "komfovent_ahu_control"
        address: 0
        command_on: 1
        command_off: 0
      - name: "Komfovent Comfort1"
        address: 99
        scan_interval: 60
        command_on: 1
        command_off: 5
      - name: "komfovent_active_mode_temperature_setpoint"
        scan_interval: 60
        address: 2032
        input_type: holding
        unit_of_measurement: °C
        scale: 0.1
        precision: 1