Why is data being erased from localStorage?

Question

JavaScript

Hello, I ran into such a problem, I have a shopping cart on Vue.js without Node, just like a library, the fact is that I store product data in localStorage:

[
{id: "16", title: "Arcturus", url: "arcturus",…},
{id: "63", title: "Alamo Frills", url: "alamo-frills",…},
{id: "88", title: "Dolores' Raspberry Sundae", url: "dolores-raspberry-sundae",…},
{id: "34", title: "Kei-Yoki", url: "kei-yoki",…}
]

For convenient work with localStorage, I took the store library. The problem is definitely not because of her, without her it was the same. There is a cart
variable :

let app = new Vue({
  el: '#app',
  data: {
         // если нет cart в localStorage, то будет пустой массив
          cart: !store.has('cart') ? [] : store.get('cart'), 
          qty: 1
        },
       ...
});

Then everything works fine, but why when I go to the site for the first time and add products to localStorage and, for example, refresh the page, everything disappears ((and if I do the same for the second time, everything is saved normally and does not disappear, tell me what could be the problem?