I can not understand why this is happening, everything should be abreast because the whole width is relative - there is no fixed place anywhere, but on sm (767-991px) this happens 
Although all the blocks are the same in essence, they break only in one place.
.product{ width: 100%; position: relative; padding-left: 15px; padding-right: 15px; &__carousel{ width: 100%; } &__item{ width: 100%; display: inline-block; vertical-align: top; position: relative; overflow-x: hidden; } &__block{ width: 100%; padding: 15px; border: 1px solid #fff; border-bottom:none; display: flex; flex-direction: column; } &__img{ width: 100%; } &__img-pos{ margin-bottom: 17px; } &__name{ font-weight: 400; text-align: center; a{ color: @gray888; font-size: 14px; text-transform: uppercase; text-decoration: none; } a:hover{ color: @green; } } &__pricebox{ text-align: center; } &__pricebox-pos{ } &__name-pos{ margin-bottom: 15px; } &__sale{ color: @gray888; text-decoration: line-through; font-size: 15px; } &__sale-pos{ margin-right: 10px; } &__price{ font-size: 20px; font-weight: 300; color: @green; } &__price-red{ color: @red; } &__stars{ color: @green; width: 100%; text-align: center; margin-bottom: 10px; } &__button{ padding: 10px 20px; } &__button-pos{ margin-bottom: 20px; } &__cart{ margin-right: 10px; } &__sprite{ width: 100%; display: flex; flex-direction: row; justify-content: center; } &__link{ display: flex; justify-content: center; align-items: center; height: 40px; width: 40px; border-radius: 50%; background-color: #f1f1f1; color: #c6c6c6; text-decoration: none !important; font-size: 18px; margin-left: 3px; margin-right: 3px; } &__link:hover{ background-color: @darkgray; color: #fff; } &__block-pos{ } &__add-block{ display: none; flex-direction: column; align-items: center; } &__add{ width: 100%; display: none; flex-direction: column; align-items: center; background-color: #fff; padding-top: 5px; padding-bottom: 25px; border: 1px solid #fff; border-top:none; } &__add-pos{ position: absolute; z-index: 4; left: 0; } &__spec-first{ top: 25px; left: 15px; } &__spec-second{ top: 51px; left: 15px; } } <div class="col-xs-12 col-sm-4 padnull"> <div class="product__item"> <div class="product__block product__block-pos"> <img class="product__img product__img-pos ware__img" src="image/men/striped_cotton_blazer_2.jpg" alt=""> <h3 class="product__name product__name-pos"><a href="" class="">STRIPED COTTON BLAZER</a></h3> <div class="product__pricebox product__pricebox-pos"> <span class="product__sale product__sale-pos">$95.00</span> <span class="product__price product__price-red">$79.00</span> </div> </div> <div class="product__add product__add-pos"> <div class="product__add-block"> <button class="button product__button product__button-pos ware__button"> <i class="fa fa-shopping-cart product__cart" aria-hidden="true"></i> add to cart</button> <div class="product__sprite"> <a href="" class="product__link"> <i class="fa fa-heart-o" aria-hidden="true"></i> </a> <a href="" class="product__link"> <i class="fa fa-share-alt" aria-hidden="true"></i> </a> </div> </div> </div> </div> </div> Here I have laid out the whole site: http://ketty.zzz.com.ua/men.html
PS I tried to replace this block, but another block became its “crooked” place.