Varying framerate (FPS) [closed]

In my game-loop, I am using fixed time step for physics and interpolation for rendering as suggested on Gaffer on Games | Fix Your Timestep!

However, when the framerate is varying between 30-60fps during the game, the game looks jumpy. For example, balls suddenly look accelerated when the frame rate increases from 35 to 45 suddenly.

Is there a way to make the game look smooth while framerate is varying?

Here is my game loop:

protected void update(float deltaTime) {
    //do some pre stuff

    deltaTimeAccumulator +=deltaTime; //deltaTimeAccumulator is a class-member holding the accumulated frame time
    while(deltaTimeAccumulator>FIXED_TIME_STEP) {
        world.step(FIXED_TIME_STEP, 6, 2);  //perform physics simulation
        deltaTimeAccumulator-=FIXED_TIME_STEP;
    }
    // world.step(deltaTime, 6, 2);

    destroyBodiesScheduledForRemoval();
    render(deltaTimeAccumulator /FIXED_TIME_STEP); //interpolate according to the remaining time
}

Here is the part related to the interpolation (related inner works of render() method) :
this.prevPosition = this.position; //get previously simulated position

    this.position = body.getPosition(); //get currently simulated position

    //interpolate
    Vector2 renderedPosition = new Vector2();
    if (prevPosition != null) {//&& !isFloatApproximatelyEquals(this.prevPosition.x, this.position.x) && !isFloatApproximatelyEquals(this.prevPosition.y, this.position.y)) {
        renderedPosition.x = this.position.x * interpolationAlpha + this.prevPosition.x * (1 - interpolationAlpha);
        renderedPosition.y = this.position.y * interpolationAlpha + this.prevPosition.y * (1 - interpolationAlpha);
    } else {
        renderedPosition = position;
    }

    //Draw the object at renderedPosition