disruption of stepper motor by tft.println, how to avoid

Hello
When (tft.println) print value on the screen every second, causes stop of stepper motor. How to avoid.

int relay1Pin = 23;   // relay
int relay2Pin = 25;
int relay3Pin = 27;
int relay4Pin = 29;
int m0 = 39;          // stepper
int m1 = 41;
int sleepPin = 47;   
const int stepPin = 49;
int dirPin = 51;

#define sclk 76    //TFT 
#define mosi 75
#define cs   10
#define dc   9
#define rst  8     

int stepPinState = LOW;           
long previous1 = 0;
long previous2 = 0;
long previous3 = 0;
long interval = 500;
static byte runStepper = 0;
static byte autoStepper = 0; 
long countImpulse = 0;
int lastStepPinState = LOW;
int stepperRev = 0;
int countDistance = 0;
int timer = 0;

#include <Keypad.h>
#include <Adafruit_GFX.h>    
#include <Adafruit_ST7735.h> 
#include <SPI.h>

Adafruit_ST7735 tft = Adafruit_ST7735(cs, dc, rst);

const byte ROWS = 4;   // four rows
const byte COLS = 4;   // four columns
// define the cymbols on the buttons of the keypads
char hexaKeys[ROWS][COLS] = {
  {
    '1','2','3','A'                      }
  ,
  {
    '4','5','6','B'                      }
  ,
  {
    '7','8','9','C'                      }
  ,
  {
    '*','0','#','D'                      }
};
byte rowPins[ROWS] = {
  22, 24, 26, 28};   // connect to the row pinouts of the keypad
byte colPins[COLS] = {
  30, 32, 34, 36};   // connect to the column pinouts of the keypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);   // initialize an instance of class NewKeypad


void setup()
{
  Serial.begin(9600);

  pinMode(relay1Pin, OUTPUT);     // relay       
  pinMode(relay2Pin, OUTPUT);
  pinMode(relay3Pin, OUTPUT);
  pinMode(relay4Pin, OUTPUT);

  pinMode(m0, OUTPUT);        // stepper
  pinMode(m1, OUTPUT);
  pinMode(sleepPin, OUTPUT);     
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  digitalWrite(m0, LOW);
  digitalWrite(m1, LOW);

  tft.initR(INITR_REDTAB);

}

void loop()
{  
  char customKey = customKeypad.getKey();

  if (customKey == '0')             // distance - reset
  {     
    countDistance = 0;
  }

  if (customKey == '1')             // relay 1 on 
  {     
    digitalWrite(relay1Pin,LOW);
  }

  if (customKey == '4')             // relay 1 off
  {     
    digitalWrite(relay1Pin,HIGH);     
  }

  if (customKey == '2')             // relay 2 on 
  {     
    digitalWrite(relay2Pin,LOW);
  }

  if (customKey == '5')            // relay 2 off
  {     
    digitalWrite(relay2Pin,HIGH);           
  }

  if (customKey == '3')             // relay 3 on 
  {     
    digitalWrite(relay3Pin,LOW);
  }

  if (customKey == '6')            // relay 3 off
  {     
    digitalWrite(relay3Pin,HIGH);           
  }   

  if (customKey == 'A')             // stepper - right direction
  {    
    runStepper = 1;
    digitalWrite(sleepPin, HIGH);
    digitalWrite(dirPin, LOW);          
  }

  if (customKey == 'B')             // stepper - left direction
  {     
    runStepper = 2;
    digitalWrite(sleepPin, HIGH);
    digitalWrite(dirPin, HIGH);     
  }

  if (customKey == 'C')    //stepper stop
  {
    runStepper = 0;
    autoStepper = 0;
    digitalWrite(sleepPin, LOW);
  }

  if (runStepper == 0)             // stepper - stand by off
  {    
    digitalWrite(sleepPin, LOW);   
  }

  if (runStepper >= 1)             // delay for a stepper
  {
    unsigned long current1 = micros();  

    if(current1 - previous1 > interval)         
    {        
      previous1 = current1;         
      if (stepPinState == LOW)       
        stepPinState = HIGH;
      else
        stepPinState = LOW;   
      digitalWrite(stepPin, stepPinState);
    }
  }

  if (customKey == 'D')       // stepper - automatic feed
  {
    autoStepper=1;
  }

  int sensorValue = analogRead(A0);    // read sensor Value
  int currentValue = sensorValue * (3.3 / 1024.0)*100;

  if (currentValue >= 244 &&  autoStepper==1)
  {
    runStepper = 3;
    digitalWrite(sleepPin, HIGH);
    digitalWrite(dirPin, HIGH);
  }

  if (currentValue < 244 && autoStepper==1)
  {
    runStepper = 0;
    digitalWrite(sleepPin, LOW);
  }

  countImpulse = 0;
  if (stepPinState != lastStepPinState) // counting steps of stepper
  { 
    if (stepPinState == HIGH)
    {  
      countImpulse = 1;
      countDistance;
      if (runStepper == 1)
      {
        countDistance = countDistance + 1;
      }
      if (runStepper == 2)
      {
        countDistance = countDistance - 1;
      }
      if (runStepper == 3)
      {
        countDistance = countDistance + 1;
      }

    }
  }
  lastStepPinState = stepPinState;

  stepperRev = (countImpulse*interval*0.54);

  if (autoStepper == 1)
  { 
    unsigned long current2 = millis();  // timer
    if(current2 - previous2 > 1000)
    { 
      timer++;
      previous2 = current2;
    }  
  }

  
  unsigned long current3 = millis();  // delay for serial monitor
  if(current3 - previous3 > 1000)
  {
    
    tft.setCursor(50, 0);
    tft.setTextColor(ST7735_WHITE);
    tft.setTextSize(1);
    tft.fillScreen(ST7735_BLACK);
    tft.println(countDistance*0.01);
    previous3 = current3;
  }
}