Solution: Last slide not getting active when 'slidePerView' set to 'auto'.

on: {
	snapGridLengthChange:function(){
		if( this.snapGrid.length != this.slidesGrid.length ){
			this.snapGrid = this.slidesGrid.slice(0);
		}
	}
}

I currently experienced the same problems like as many people did and also looked through the issues but no results. #2571, #1257, #534 Finally, I found out a way to do it, a better way to do it guys!.

By setting the snapGrid settings as same as the slidesGrid settings after the swiper initialized. And then the swiper will work as what you expected.

const swiper = new Swiper(
    '.awesome-swiper', 
    {
        init: false,
        direction: 'horizontal',
        speed: 700,
        slidesPerView: 'auto',
        spaceBetween: 80,
    }
);

swiper.init();
swiper.snapGrid[swiper.snapGrid.length - 1] = swiper.slidesGrid[swiper.slidesGrid.length - 1];

or even completely replacing it by cloning the settings.

// can do this way
swiper.snapGrid = swiper.slidesGrid.slice(0);

// or ES6 way
swiper.snapGrid = [...swiper.slidesGrid];

this work for me, but with a little adjustment: I placed this line this.snapGrid = [...this.slidesGrid]; inside of the reachEnd swiper event, like this:

const swiper = new Swiper('.awesome-swiper', {
    direction: 'horizontal',
    speed: 700,
    slidesPerView: 'auto',
    spaceBetween: 80,
    on: {
      reachEnd: function() {
        this.snapGrid = [...this.slidesGrid];
      },
    }
}