Why is my v-checkbox not changing visually on click?

So logic is working as intended but my checkbox is not switching between states when clicked. As far as i know v-checkbox does not need to have v-model or value set.All i need is visuall checkbox effect.

 <v-list-item-group>
   <template v-for="(item, index) in items">

     <v-list-item 
      :key="index" 
      :to="{
        path: `/${$store.state.selectedOffice.id}/contacts/edit/${item.id}?type=edit`,
        query: $route.query
           }"
      :class="selectedContacts.find(x => x === item.id) ? 'selectedItem' : null">
          <v-checkbox 
            v-if="showCheckboxes" 
            @click.self.prevent="addToContactsGroup(item.id)">
          </v-checkbox>

I guess it has something to do with event above him that does not allow checkbox state to change. If i move checkbox outside it works.