Poor quality of communications

[SoUtHeaST41]

I am using modbus tk to simulate a slave on a raspberry pi with the following code:
`import modbus_tk
import modbus_tk.defines as cst
from modbus_tk import modbus_rtu
import serial
import time

PORT = "/dev/ttyUSB0"

def main():
"""main"""
#Create the server
server = modbus_rtu.RtuServer(serial.Serial(PORT,baudrate=9600,bytesize=8,parity='N', stopbits=1))
t = 32

try:
    server.start()

    slave = server.add_slave(8)

    slave.add_block('0', cst.HOLDING_REGISTERS, 0, 10)
 
    slave.set_values('0', 0, [t, 87, 255, 0, 1, 0, 1, 1,22])
  
    while True:
        values = slave.get_values('0', 0, 10)
        
        print('values read: %s\r\n' % (str(values)))
        print("wait for a while...")
        time.sleep(1)
            

finally:
    server.stop()

if name == "main":
main()
Use modbus poll at the PC to simulate the master reading and writing to the slave registers.
However, the quality of communications has been poor, with a ratio of successful communications to communications timeouts of about 2 to 1.

Please point out my problem or include it in the next version of the upgrade!