Manage TWO serial ports by HASSIO

Configuration
1

Hello i need your support for manage TWO serial comunication with Hassio x RPI 4 connected to USBs ports

One is by modbus that running correctly this is the configuration

modbus:
  name: plc
  type: serial
  method: rtu
  port: /dev/ttyUSB0
  baudrate: 9600
  stopbits: 1
  bytesize: 8
  parity: N

The second i need send some strings (ande receive) to serial port other USB with
shell command, for this i use serial platform.

sensor:
  - platform: serial
    serial_port: /dev/ttyUSB1

switch:
  - platform: command_line
    switches:
      modem1_at:
        command_on: echo -e -n "ATE1\r" > /dev/ttyUSB1
        command_off: echo -e -n "AT+CMGF=1\r" > /dev/ttyUSB1

For both i use a suitable adapter usb -> RS232.

If use one system only with usb0 it all ok, but when i try both with Modbus USB0 and Shell command with USB1 the second fail.

I made some tests and i was suprise that if i move the adapter from fisical port
USB0 to USB1 (but the yaml file doesn’t touch - port: /dev/ttyUSB0) the modbus running in correct way, it seem that USBx is not relative to fiscal port Could be ?

So Can you suggest to me in what way i can manage two serial comunication ? (USB port or alternative GPIO Tx & RX).

Thanks in advance, and a great new year.

Paolo