Writing data to nextion display make interrupt on stepper motor

Question

I want to read temp from two max6675 and print on nextion display and at the same time stepper motor working as well , but the problem is writing data to nextion make interrupt on stepper motor , can anyone help me ?

#include <Stepper.h>
#include "EasyNextionLibrary.h" 
#include "max6675.h"


const int stepsPerRevolution = 200;  // change this to fit the number of steps per revolution
// for your motor

const int REFRESH_TIME = 100;           
unsigned long refresh_timer = millis();  



float dtempc = 0.0f;
float dtempf = 0.0f;
float btempc = 0.0f;
float btempf = 0.0f;


//============Drum Pin Temp digital pin in atmega============
int thermoDO = 4; 
int thermoCS = 5; 
int thermoCLK = 6; 
int thermoDO1 = 7; 
int thermoCS1 = 8; 
int thermoCLK1 = 9; 


EasyNex myNex(Serial); 
MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);
MAX6675 thermocouple1(thermoCLK1, thermoCS1, thermoDO1);



// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 10, 11, 12, 13);

int stepCount = 0;  // number of steps the motor has taken

void setup() {
  // nothing to do inside the setup
  myNex.begin(9600); 
}

void loop() {

  myNex.NextionListen();
  // read the sensor value:
  int sensorReading = analogRead(A0);
  // map it to a range from 0 to 100:
  int motorSpeed = map(sensorReading, 0, 1023, 0, 100);
  // set the motor speed:
  if (motorSpeed > 0) {
    myStepper.setSpeed(motorSpeed);
    // step 1/100 of a revolution:
    myStepper.step(stepsPerRevolution / 100);
  }
  printonnextion();
  
}

void printonnextion(){

    if((millis()-refresh_timer) > REFRESH_TIME)
  {
    dtempc = thermocouple.readCelsius();
    dtempf = thermocouple.readFahrenheit();
    btempc = thermocouple1.readCelsius();
    btempf = thermocouple1.readFahrenheit();
    myNex.writeStr("dtempc.txt", String(dtempc)+"C"); 
    myNex.writeStr("dtempf.txt", String(dtempf)+"F"); 
    myNex.writeStr("btempc.txt", String(btempc)+"C"); 
    myNex.writeStr("btempf.txt", String(btempf)+"F");  
    myNex.writeNum("drumtemp.val", dtempc);
    myNex.writeNum("beantemp.val", btempc);
   
    
    refresh_timer = millis();  
    
  } 

  }

but the problem is writing data to nextion make interrupt on stepper motor , can anyone help me ?