I have created a chat app using live views in which whenever user joins a chatroom then all the messages of the chat room displayed to him that are saved in database and if some updates or edit any message it works perfect everyone sees the updated message but sometimes it misses some user screens specially if some leave a chat room open for few hours then the that user stops receiving updates and he need to refresh browser even sometimes browser refresh don’t work
Here is my code in my live view for chat

defmodule FchatappWeb.ChatLive do
  use FchatappWeb, :live_view
  alias Fchatapp.Blog
  alias Fchatapp.Blog.Room
  alias Fchatapp.Repo
  alias Fchatapp.Chats.Message
  import Ecto.Query, only: [from: 2]

  @imp true
  def mount(%{"room" => name}, session, socket) do
    room_data = Repo.get_by(Room, title: name)
    room_data_id = room_data.id

    query =
      from m in Message,
        where: m.room_id == ^room_data_id

    db_messages = Repo.all(query)
    topic = "room:" <> name

    email =
      case session["current_user"] do
        nil ->
          "Anonymous User"

        _ ->
          session["current_user"].email
      end

    anonymous_user =
      case email do
        "Anonymous User" ->
          true

        _ ->
          false
      end

    if connected?(socket) do
      Process.send_after(self(), %{event: "update", room_id: room_data_id}, 5000)
      FchatappWeb.Endpoint.subscribe(topic)
      FchatappWeb.Presence.track(self(), topic, email, %{})
    end

    {:ok,
     assign(socket,
       room: name,
       room_id: room_data.id,
       image: room_data.image_thumb_url,
       country: room_data.country,
       state: room_data.state,
       city: room_data.city,
       description: room_data.description,
       topic: topic,
       user: email,
       anonymous_user: anonymous_user,
       message: "",
       image_public_id: "",
       image_thumb_url: "",
       image_url: "",
       image_secure_url: "",
       img_context: "",
       messages: db_messages,
       user_list: [],
       temporary_assigns: [messages: []]
     )}
  end

  @imp true
  def handle_event(
        "submit_message",
        %{
          "_csrf_token" => _token,
          "chat" => %{
            "message" => message,
            "image_public_id" => image_public_id,
            "image_thumb_url" => image_thumb_url,
            "image_url" => image_url,
            "image_secure_url" => image_secure_url,
            "room_id" => room_id,
            "img_context" => img_context
          }
        },
        socket
      ) do
    message = %{
      uid: UUID.uuid4(),
      content: message,
      user: socket.assigns.user,
      image_public_id: image_public_id,
      image_thumb_url: image_thumb_url,
      image_url: image_url,
      image_secure_url: image_secure_url,
      room_id: room_id,
      img_context: img_context
    }

    case image_url do
      "" ->
        {:ok}

      _ ->
        resp =
          HTTPoison.post(
            "http://localhost:4000/api/create-message",
            message |> Poison.encode!(),
            %{"Content-Type" => "application/json"}
          )
    end

    FchatappWeb.Endpoint.broadcast(socket.assigns.topic, "new-message", message)

    {:noreply,
     assign(socket,
       message: "",
       image_public_id: "",
       image_thumb_url: "",
       image_url: "",
       image_secure_url: ""
     )}
  end

  @imp true
  def handle_event(
        "form_update",
        %{
          "_csrf_token" => _token,
          "chat" => %{
            "message" => message,
            "image_public_id" => image_public_id,
            "image_thumb_url" => image_thumb_url,
            "image_url" => image_url,
            "image_secure_url" => image_secure_url,
            "room_id" => room_id,
            "img_context" => img_context
          }
        },
        socket
      ) do

    {:noreply,
     assign(socket,
       message: message,
       image_public_id: image_public_id,
       image_thumb_url: image_thumb_url,
       image_url: image_url,
       image_secure_url: image_secure_url,
       room_id: room_id,
       img_context: img_context
     )}
  end

  @imp true
  def handle_info(%{event: "new-message", payload: message}, socket) do
    {:noreply, assign(socket, messages: [message])}
  end

  def handle_info(%{event: "update", room_id: id}, socket) do
    Process.send_after(self(), %{event: "update", room_id: id}, 5000)

    query =
      from m in Message,
        where: m.room_id == ^id

    db_messages = Repo.all(query)
    {:noreply, assign(socket, messages: db_messages)}
  end

  def handle_info(%{event: "presence_diff", payload: %{joins: joins, leaves: leaves}}, socket) do
    join_messages =
      joins
      |> Map.keys()
      |> Enum.map(fn username ->
        %{uid: UUID.uuid4(), content: "#{username} Joined!", user: "System"}
      end)

    leave_messages =
      leaves
      |> Map.keys()
      |> Enum.map(fn username ->
        %{uid: UUID.uuid4(), content: "#{username} Left!", user: "System"}
      end)

    user_list =
      FchatappWeb.Presence.list(socket.assigns.topic)
      |> Map.keys()

    {:noreply, assign(socket, user_list: user_list)}
  end

  def display_message(%{uid: id, content: content, user: "System"}) do
    ~E"""
    <p id="<%= id %>"><em><%= content %></em></p>
    """
  end

  def display_message(
        %{
          uid: id,
          content: content,
          user: user,
          image_public_id: image_public_id,
          image_thumb_url: image_thumb_url,
          image_url: image_url,
          image_secure_url: image_secure_url
        } = params
      ) do
    case image_url do
      "" ->
        ~E"""
        <div id="<%= id %>">
        <img src="https://media.istockphoto.com/vectors/emoticon-with-sorry-sign-vector-id1266144552?k=20&m=1266144552&s=170667a&w=0&h=m-3MDOgzYDjsynL729p7G8Pn98PNKLu345LnFwkcZlY=" width="100" height="150"></img>
        <p><em>Image cant be empty</em></p>
        </div>

        """

      _ ->
        ~E"""
        <div id="<%= id %>">
        <div><img src="<%= image_url%>" width="100" height="150"></img>
        <p><strong><%= user%>: </strong><%= content %> </p>
        </div>
        </div>
        """
    end
  end
end

Here is template hidden inputs are coming from an api

<section>

    <div id="header-text">
        <div id="title">
        <p >Currently Chatting In <strong><%= @room %></strong></p>
        <p ><img src="<%= @image %>" alt="no-image"></p>
        <p ><%= @description %></p>
        <button><a href="/">Leave Room</a></button>
        </div>
    </div>
    <br>

    <div id="main">
        <div class="sub-main">
            <div id="chat-container">
                <div id="messages-container" phx-update="append">
                    <%= for message <- @messages do%>
                    <%= display_message(message) %>
                    <% end %>
                </div>
            </div>
            <%= if @anonymous_user do %>
            <p><strong><em>Please login to send messages</em></strong></p>
            <% else %>
            <div id="form-chat">
                <%= f = form_for :chat, "#", id: "chat-form", phx_submit: :submit_message, phx_change: :form_update %>
                <%= text_input f, :message, value: @message, placeholder: "Enter your message..." %>
                <%= hidden_input f, :image_public_id, value: @image_public_id, id: "image_public_id"  %>

                <%= hidden_input f, :image_thumb_url, value: @image_thumb_url, id: "image_thumb_url" %>

                <%= hidden_input f, :image_url, value: @image_url, id: "image_url" %>

                <%= hidden_input f, :image_secure_url, value: @image_secure_url, id: "image_secure_url" %>
                <%= hidden_input f, :room_id, value: @room_id, id: "room_id" %>
                <%= hidden_input f, :img_context, value: @img_context, id: "img_context" %>
                <!-- placeholder for uploaded image -->
                <img
                        id="uploadedimage"
                        src="<%= @image_thumb_url %>">
                </img>
                <button
                        id="upload_widget"
                        class="cloudinary-button" type="button">
                    Upload New Image
                </button>

                </form>
            </div>
            <% end %>
        </div>

    <div id="users">
        <h3>
            Online User
        </h3>
        <%= for user <- @user_list do%>
            <p><%= user %></p>
        <% end %>
    </div>
    </div>


</section>

Thanks in advance