Vue-MultiSelect: Can't seem to get property from an object during select event

I am using the Vue-Multiselect plugin for an input drop down box and trying to get the customer's last name when they fill out a form. For some reason I am just getting an object as the value of the issue.customer_last_name property (see screenshot below). I want to get a string Doe, instead.

Anyone have any ideas ? My goal is to eventually submit this data (POST request) via a submit button to a remote api.

Link to codesandbox replicating the issue: https://codesandbox.io/s/vue-template-9z1wd?fontsize=14&module=%2Fsrc%2Fcomponents%2FTest.vue

Full code:

<template>
  <div>
    <label for="customer_last_name_input">Last Name:</label>
    <multiselect
      id="customer_last_name_input"
      v-model="issue.customer_last_name"
      :options="customers"
      placeholder="Select an existing customer or type to add a new one"
      :custom-label="customerSelectName"
      label="lastname"
      track-by="uid"
      :close-on-select="true"
      @select="onSelect"
    ></multiselect>
    <br>
    <!-- <input id="customer_last_name_input" type="text" class="form-control" v-model="issue.customer_last_name" placeholder required /> -->
    <div>
      <label for="customer_first_name_input">First Name:</label>
      <input
        id="customer_first_name_input"
        type="text"
        v-model="issue.customer_first_name"
        placeholder
        required
      >
    </div>
  </div>
</template>

<script>
import Multiselect from "vue-multiselect";
export default {
  name: "test",
  components: {
    Multiselect
  },
  data() {
    return {
      customers: [
        {
          uid: "1",
          firstname: "John",
          lastname: "Doe",
          email: "johndoe@aol.com",
          phone: null,
          c_organization: "ACME",
          c_title: null
        },
        {
          uid: "2",
          firstname: "Mary",
          lastname: "Smith",
          email: "msmith@aol.com",
          phone: null,
          c_organization: "NBA",
          c_title: "Miss"
        }
      ],
      issue: {
        customer_first_name: "",
        customer_last_name: ""
        //customer_email: ""
      }
    };
  },
  // async created() {
  //   await this.getCustomers()
  // },
  methods: {
    customerSelectName(option) {
      //return `${option.lastname}, ${option.firstname}`
      return `${option.lastname}, ${option.firstname}`;
    },
    onSelect(option) {
      console.log(option.lastname);
      this.issue.customer_last_name = option.lastname;
      this.issue.customer_first_name = option.firstname;
      // this.issue.customer_email = option.email
    }
  }
};
</script>

The problem is the v-model="issue.customer_last_name" on the multi-select itself. That's setting the selection of the multi-select component to the whole object that the user selects, not just the last name.

Since you're using @select="onSelect" to do all the updating necessary, just remove the v-model (line 6 in the code sandbox) and you'll be all set.

Edited to add:

When you're seeing unhelpful [object Object], it can be useful to render that somewhere else, where it's more likely to be fully expanded. It's all somewhat browser dependent, but adding <div>{{issue.customer_last_name}}</div> was a helpful debugging tool.