Why does offsetTop always have the same value?

Question

Vue.js

I am using tab method like here https://vuejs.org/v2/guide/components-dynamic-asyn...

<keep-alive>
  <component v-bind:is="currentTabComponent"></component>
</keep-alive>

But in my two tabs everything works fine autoscroll, but in one place it does not want to change. Let me tell you what I mean

watch: {
            scroll(value) {
                if (value) {//Если значение true то нужно сделать автоскролл
                    this.$nextTick(() => {
                        let el = document.getElementsByClassName("tab-body scrolling")[0];
                        el.scrollTop = this.$refs[this.itemName].offsetTop - this.$refs[this.itemName].scrollHeight;
//В итоге выходит в той вкладке которая проблемная, el.scrollTop = 0; 
// this.$refs[this.itemName].offsetTop = 729
//this.$refs[this.itemName].scrollHeight = 205
                    });
                }
            },
        },

And if you don't change the scrollTop even in the browser, then nothing changes. I don't understand why it is so. The tab-body scrolling class is the same for all of these tabs.