Pi4 RTS pin big delay

Question

I am trying to use modbus with RS485 on my Pi4. I'm using modbus_tk with pySerial library, and I managed to get controllig RTS pin while transmitting data, but I cant get it running faster - when TX ends the pins stays UP for aprox. 30ms (25 +- 35) after TX.

My code below:

socket = serial.rs485.RS485(port=PORT, baudrate=460800, bytesize=8, parity='N', stopbits=1, rtscts=True, dsrdtr=False, timeout=0.01, xonxoff=0 )
socket.rs485_mode = serial.rs485.RS485Settings(rts_level_for_tx=True, rts_level_for_rx=False, loopback=False, delay_before_tx=0, delay_before_rx=0)

master = modbus_rtu.RtuMaster(socket)

master.set_timeout(2.0)
master.set_verbose(True)
def readAll():
    try:
        data = master.execute(1, cst.READ_HOLDING_REGISTERS, 999, 55)
        os.system('clear')
        print(datetime.now())
        print("IsolInputs: ", data[0:4])
        print("ADCInputs: ", data[4:21])
        print("ADCInputs_raw: ", data[21:37])
        print("RelayOtuputs: ", data[37:43])
        print("PWMFrequency: ", data[43])
        print("PWMDutyCycle: ", data[44:54])
        print("DevStatus: ", data[54])

    except modbus_tk.modbus.ModbusError as exc:
        logger.error("%s- Code=%d", exc, exc.get_exception_code())

I tried to manually control another GPIO Pin via hooks in modbus_tk lib, but it gives me the simmilar result:

def on_before_write(args):
    GPIO.output(EN_485, GPIO.HIGH)
hooks.install_hook("modbus.Master.before_send", on_before_write)

def on_after_write(args):
    GPIO.output(EN_485,  GPIO.LOW)
hooks.install_hook("modbus.Master.after_send", on_after_write)

Any ideas?

Thanks!