Computed property returns empty array, despite there being data in the array

I need help figuring out why my computed property is returning an empty array.

Let me explain:

My EditPost.vue file has data like so:

data() {
    return {
      posts: [
        {
          post_id: 1,
          process_id: 4,
          post_name: "ACME Widget",
          poc_list: [1, 2]
        },
        {
          post_id: 2,
          process_id: 1,
          post_name: "XYZ Widget",
          poc_list: 3
        },
        {
          post_id: 3,
          process_id: 2,
          post_name: "ABC Bar",
          poc_list: null
        },
        {
          post_id: 4,
          process_id: 3,
          post_name: "Foo Bar",
          poc_list: [1, 3]
        }
      ],
userProfiles: [
        {
          uid: 1,
          firstname: "Claiborne",
          lastname: "Heberden",
          email: "cheberden0@gravatar.com"
        },
        {
          uid: 2,
          firstname: "Gerick",
          lastname: "Tetla",
          email: "gtetla1@whitehouse.gov"
        },
        {
          uid: 3,
          firstname: "Raymund",
          lastname: "Espy",
          email: "respy2@freewebs.com"
        },
        {
          uid: 4,
          firstname: "Dilly",
          lastname: "Dimitriev",
          email: "ddimitriev3@skype.com"
        },
...snip...
      ],

with a computed property like so:

  computed: {
    contacts() {
      const contacts = this.userProfiles.filter(
        contact => this.posts.poc_list === contact.uid
      );
      return contacts;
    }
  }

Despite the posts array containing values for some of the poc_lists properties, the computed property contacts is not returning the values.

Full demo here : Click POSTS -->Edit (next to ACME WIDGET) and you'll see "Current Contacts" section is not populated, despite there being data.

Thanks for any help anyone can provide!