2023.7.3 - issue with modbus blocking other devices (openwb, Alpha-ESS)

Hello there… I’ve stumpled over a modbus tcp issue, all ideas and tipps appreciated !

Setup: HA 2023.7.3 (docker), a Alpha-ESS Smile T10 solar inverter/battery and a openwb wallbox.

the openwb connects via modbus/tcp to the Alpha-ESS to check for available PV power etc. works fine, and I can still see port 502 on the Alpha-ESS as “open” and do a manual “mbpoll” to read data.

I started to monitor the Alpha-ESS with HA (using snitzelweck92 / homeassistant_alphaess_modbus_tcp ). This works great, but as soon as HA is using this modbus setup, the openwb can not access data from the Alpha-ESS anymore, and a nmap shows that port 502 on the Alpha-ESS is closed…

As soon as HA is stopped, the port 502 is again “open” and openwb picks up readings again.

My guess is that HA does not close the modbus connection in between polls (every 20 sec). Are there any timings/settings that can be used to close the modbus connection directly after a poll ?

my modbus config is:

modbus:
  - name: modbuspvsystem
    type: tcp
    host: !secret alphaess_modbus_host_ip
    port: !secret alphaess_modbus_host_port
    message_wait_milliseconds: 0 # waittime between 2 messages
    timeout: 1 # timeout in seconds before connection is closed
    retry_on_empty: true
    delay: 0 # delay in seconds at startup

    #definition of sensors
    sensors:
      # BATTERY
      #SOC
      - name: Alpha ESS SOC Battery
        unique_id: PV_SOC_Battery
        slave: !secret alphaess_modbus_slaveId
        address: 258
        input_type: holding
        count: 1
        data_type: int16
        unit_of_measurement: "%"
        device_class: battery
        state_class: measurement
        scan_interval: 20
        scale: 0.1
        precision: 2