the ball does not function as desired when clicked on the desired button, Phaser 3

[arif]

there seems to be something wrong with the code, one button has to slow down and one button to speed up when I add this code,
 

this.downButton = this.add.image(80, 530, 'up-bubble').setInteractive();
    this.upButton = this.add.image(230, 530, 'down-bubble').setInteractive();
    this.input.on('gameobjectup', function (pointer, gameobject) {

        if (gameobject === this.downButton && this.spinSpeed > 0)
        {
            this.spinSpeed -= 0.1;
        }
        else if (gameobject === this.upButton && this.spinSpeed < 9.9)
        {
            this.spinSpeed += 0.1;
        }

    });   

but, when I add this code between generateBalls (), it doesn't work at all, it doesn't work,

generateBalls() {

    const hitArea = new Phaser.Geom.Rectangle(0, 0, 32, 32);
    const hitAreaCallback = Phaser.Geom.Rectangle.Contains;        

    const circle = new Phaser.Geom.Circle(400, 300, 220);
    const balls  = this.add.group(null, { 
        key: 'balls', 
        frame: [0, 1, 5], 
        repeat: 5, 
        setScale: { x: 3, y: 3 },
        hitArea: hitArea,
        hitAreaCallback: hitAreaCallback,
    });

    this.downButton = this.add.image(80, 530, 'up-bubble').setInteractive();
    this.upButton = this.add.image(230, 530, 'down-bubble').setInteractive();
    this.input.on('gameobjectup', function (pointer, gameobject) {

        if (gameobject === this.downButton && this.spinSpeed > 0)
        {
            this.spinSpeed -= 0.1;
        }
        else if (gameobject === this.upButton && this.spinSpeed < 9.9)
        {
            this.spinSpeed += 0.1;
        }

    });       

    Phaser.Actions.PlaceOnCircle( balls.getChildren(), circle);
    return balls;
}
 generateDance() {
        this.spinSpeed = 0.003;  
        return this.tweens.addCounter({
            from: 220,
            to: 160,
            duration: 9000,
            delay: 2000,
            ease: 'Sine.easeInOut',
            repeat: -1,
            yoyo: true
        });
    }
update() {

    this.playerEyes.update();
    Phaser.Actions.RotateAroundDistance( this.balls.getChildren(), { x: 400, y: 300 }, this.spinSpeed, this.dance.getValue());
}

I took the code from the Phaser 3 example this is https://phaser.io/examples/v3/view/tweens/tween-time-scale