Phaser 3 Pixel flicker effect

On mobile device same odd pixel flicker effect is visible at the button if the background is turnd on.

by ragesoft

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/phaser/3.55.2/phaser.min.js"></script>
<div id="main">  
  <div id="game">
  
  </div>
</div>

CSS

body, html{
  height: 100%;
}
#main{
  max-width: 100%;
  max-height: 100%;
}

JavaScript

var config = {
	parent: 'game',
  scale:{
  	mode: Phaser.Scale.FIT,
    fullscreenTarget: 'game', //'main',
    autoCenter: Phaser.Scale.CENTER_BOTH,
  },
  dom: {
    createContainer: true,
  },
  fps: {
    target: 30,
  },
  width: 1366,
  height: 768,
  scene: {
  	preload: preload,
  	create: create,
    update: update,
  }
};
const fontStyles = {
    'dialogtitle': {
        fontSize: '28px',
        fontStyle: 'bolder',
        fill: '#AFAFAF' 
    },
    'default':{
        fontSize: '20px',
        fontStyle: '',
        fill: '#565353',
        wordWrap: {
        	useAdvancedWrap: true,
        }
    },
    'button':{
        fontSize: '20px',
        fontStyle: '',
        fill: '#cccac6' 
    },
}

function preload(){
        let pos = {
            x: this.game.config.width / 2,
            y: this.game.config.height / 2 + 140,
            w: 200,
            h: 40,
            b: 2,
        }
        // loading bar
        var progressBar = this.add.graphics();
        var progressText = this.make.text();
        progressText.setPosition(pos.x, pos.y + pos.h + 5)
            .setOrigin(0.5);
        this.load.on( 'progress', ( value ) => {
            progressBar.clear();
            progressBar.fillStyle( 0xffffff, 1);
            progressBar.fillRect(pos.x - pos.w/2, pos.y - pos.h/2, pos.w, pos.h );
            progressBar.fillStyle( 0xff0000, 1);
            progressBar.fillRect(pos.x - pos.w/2 + pos.b, pos.y - pos.h/2 + pos.b, value*( pos.w - 2*pos.b), pos.h - 2*pos.b);
        });
        this.load.on( 'fileprogress', ( file ) => {
            let folder = String(file.url).split("/");
            progressText.setText(folder[ folder.length - 2]);
            
        });
        this.load.on( 'complete', () => {
            progressBar.destroy();
            progressText.destroy();
        });
        
	this.load.image("dlg_background", "https://i.ibb.co/MRdSbdN/background-parchment.png");
  this.load.image("dlg_corner",...