问为什么Rails6刺激反射会重新渲染包含重复内容的页面？

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    <%= block_card title: 'BILLING', footer: (link_to('Add Billing Detail', new_project_billing_detail_path(@project)) if policy(@project.billing_details.new).new?) do %>
      <%= @alert %>
        <%= form_with model: @billing_detail, html: { novalidate: true }, data: { reflex: "submit->BillingDetailReflex#submit" } do |form| %>
          <% if @billing_detail.errors.any? %>
            <% @billing_detail.errors.full_messages.each do |message| %>
              <%= tag.li message %>
            <% end %>
          <% end %>
          <div>
            <%= form.text_field :date, 
              placeholer: 'Date',
              required: true,
              data: { reflex: "change->BillingDetailReflex#submit" } %>

            <%= form.text_field :billing_code, 
              placeholer: 'Billing Code',
              required: true,
              data: { reflex: "change->BillingDetailReflex#submit" } %>

            <%= form.text_field :project_id %>
            <%= form.text_field :user_id, value: current_user.id %>
          </div>          
          <%= form.submit %>
        <% end %>
<% end %>

# frozen_string_literal: true

class BillingDetailReflex < ApplicationReflex
  before_reflex do
    @billing_detail = BillingDetail.new
    @billing_detail.assign_attributes(billing_detail_params)
  end

  def submit
    if @billing_detail.save!
      @alert = "saved id:#{ @billing_detail&.id }"
    else
      @alert = 'NOT saved'
    end
  end

  private

  def billing_detail_params
    params.require(:billing_detail).permit(
      :date,
      :billing_cycle,
      :user_id,
      :project_id
    )
  end
end