Question Simtools does not send a new signal after 1 minute of operation.

I have a 2 dof simulator project using Simtools to send signals to Arduino but when playing or testing in output testing, the signal can only be sent for about 1 minute then simtools does not send any new signals to Arduino anymore, but when I check the LCD displaying the Pitch, Roll, etc. values, Arduino is still connected but all data freezes at the last values it received before stopping.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <PID_v1.h>


#define MP1 10 // PWM CW
#define MP2 11 // PWM CCW
#define ML1 6 // PWM CW
#define ML2 9 // PWM CCW


#define POT_R A0
#define POT_L A1


char buffer_data = 0;
int buffercount = -1;
byte commandbuffer[7] = {0};


int pitch = 0, sway = 0, roll = 0;
double err_L, err_R, err_sway, err_roll, err_pitch;
double motor_R = 100;
double motor_L = 100;

// -------------------- LCD ------------------------------
LiquidCrystal_I2C lcd(0x27,20,4);

// -------------------- PID ------------------------------
double inputR, outputR, setpointR;
double input, output, setpoint;
double kp = 2.8, ki = 20 , kd = 0;

PID pidRight(&inputR, &outputR, &setpointR, kp, ki, kd, DIRECT);
PID pidL(&input, &output, &setpoint, kp, ki, kd, DIRECT);
void setup() {
Serial.begin(115200);

lcd.init();
lcd.backlight();
lcd.setCursor(0,0);
pinMode(POT_R, INPUT);
pinMode(MP1, OUTPUT);
pinMode(MP2, OUTPUT);
pinMode(POT_L, INPUT);
pinMode(ML1, OUTPUT);
pinMode(ML2, OUTPUT);
pidL.SetMode(AUTOMATIC);
pidL.SetSampleTime(10);
pidL.SetOutputLimits(-255, 255);
pidRight.SetMode(AUTOMATIC);
pidRight.SetSampleTime(10);
pidRight.SetOutputLimits(-255, 255);


}

void loop(){
readSimTools();
process_signal();
MotorLeft();
MotorRight();
showLCD();

}


void readSimTools()

{
while(Serial.available())
{
if(buffercount==-1)
{
buffer_data = Serial.read();
if(buffer_data =='S')
{// Start game
buffercount=-1;
}
else if(buffer_data =='E')
{ //End game
buffercount=-1;
}
else if(buffer_data =='P')
{ //"P" is the marquer. If we read P, the next data is pitch

buffercount=0;
}
}
else // if(buffercount>=0)
{
buffer_data = Serial.read();
commandbuffer[buffercount]=buffer_data; // The first value next to "P" is saved in commandbuffer in the place "buffercount"
buffercount++;
if(buffercount > 6)
{
if(commandbuffer[6]=='C') // If the third data is "C", then commandbuffer is full, we can use it
{
pitch=(commandbuffer[0])*256+commandbuffer[1];
sway=(commandbuffer[2])*256+commandbuffer[3];
roll=(commandbuffer[4])*256+commandbuffer[5];
//ma
sway=map(sway,0,1023,0,200);
pitch=map(pitch,0,1023,0,200);
roll=map(roll,0,1023,0,200);
}
buffercount=-1; // Re-initialize buffercount.
}
}
}
}

void process_signal()
{
err_pitch = pitch-100; //pitch = len doc
err_sway = sway-100; //sway = trai phai
err_roll = roll-100; //roll = xoay vong
//truyen dong co
err_R= 2*err_pitch - 3*err_sway + err_roll;
err_L= 2*err_pitch + 3*err_sway - err_roll;
motor_R=100 + err_R;
motor_L=100 + err_L;


if(motor_R>160) motor_R=160;
else if(motor_R<40) motor_R=40;
if(motor_L>160) motor_L=160;
else if(motor_L<40) motor_L=40;


}




void MotorLeft(){
int rawPotL = analogRead(POT_L);
input = map(rawPotL, 0, 1023, 0, 360);
setpoint = motor_L;
pidL.Compute();

if(output > 10){
analogWrite(MP1, output);
analogWrite(MP2, 0);

} else if(output < -10){

analogWrite(MP1, 0);
analogWrite(MP2, abs(output));

} else {
analogWrite(MP1, 0);
analogWrite(MP2, 0);
}
}


void MotorRight(){
int rawPotR = analogRead(POT_R);
inputR = map(rawPotR, 0, 1023, 0, 360);
setpointR = motor_R;
pidRight.Compute();

if(outputR > 10){
analogWrite(ML1, outputR);
analogWrite(ML2, 0);

} else if(outputR < -10){
analogWrite(ML1, 0);
analogWrite(ML2, abs(outputR));

} else {
analogWrite(ML1, 0);
analogWrite(ML2, 0);
}
}

// =========== 3. Hiển thị LCD =========================
void showLCD(){
lcd.setCursor(0,0);
lcd.print("P:"); lcd.print(pitch); lcd.print(" S:"); lcd.print(sway);
lcd.setCursor(0,1);
lcd.print("R:"); lcd.print(roll); lcd.print(" Pot:"); lcd.print((int)inputR);lcd.print("/");
lcd.setCursor(0,2);
lcd.print("SP:"); lcd.print((int)setpointR);lcd.print("/"); lcd.print(" "); lcd.print((int)outputR);lcd.print("/");
lcd.setCursor(0,3);
lcd.print("MR:"); lcd.print(analogRead((int)POT_R)); lcd.print(" ML:"); lcd.print(analogRead((int)POT_L));

Serial.print(setpointR);
Serial.print(" ");
Serial.print(inputR);
Serial.print(" ");
Serial.println(outputR);
}