[Ruby on Rails]フォームからの商品一括登録機能実装におけるエラーハンドリングができません

class Form::ProductCollection < Form::Base
  FORM_COUNT = 10 #ここで、作成したい登録フォームの数を指定
  attr_accessor :products 

  def initialize(attributes = {})
    super attributes
    self.products = FORM_COUNT.times.map { Product.new() } unless self.products.present?
  end

  def products_attributes=(attributes)
    self.products = attributes.map { |_, v| Product.new(v) }
  end

  def save
    Product.transaction do
      self.products.map do |product|
        if product.availability # ここでチェックボックスにチェックを入れている商品のみが保存される
          product.save
        end
      end
    end
      return true
    rescue => e
      return false
  end
end

class Form::Base
  include ActiveModel::Model
  include ActiveModel::Callbacks
  include ActiveModel::Validations
  include ActiveModel::Validations::Callbacks

end

class Product < ApplicationRecord
  with_options presence: true do
    validates :item_number, length: { maximum: 11 }
    validates :name, length: { maximum: 50 }
    validates :color
    validates :price, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
    validates :availability, inclusion: { in: [true, false] }
  end

  validates :note, length: { maximum: 50 }
end

class ProductsController < ApplicationController

  def new
    @form = Form::ProductCollection.new
  end

  def create
    @form = Form::ProductCollection.new(product_collection_params)
    if @form.save
      redirect_to new_product_path
    else
      render :new
    end

  end

  private

    def product_collection_params
        params.require(:form_product_collection)
        .permit(products_attributes: [:item_number, :name, :color, :price, :note, :availability])
    end

end

<%= form_for(@form, url: products_path, method: :post) do |fb| %>
<div class="container">

<%= render partial:'error_messsages', model: fb.object %>

<table class="table">
<thead>
  <tr>
    <th width="60px">登録</th>
    <th>品番</th>
    <th>商品名</th>
    <th>色</th>
    <th>販売価格</th>
    <th>備考</th>
  </tr>
</thead>
<tbody class="bulk-registration-form">
<%= fb.fields_for :products do |f| %>
  <tr class="item">
  <td class="text-center">
  <%= f.check_box :availability, class: 'top10 registration-checkbox' %>
  </td>
  <td>
  <%= f.text_field :item_number, class: 'form-control' %>
  </td>
  <td>
  <%= f.text_field :name, class: 'form-control' %>
  </td>
  <td>
  <%= f.text_field :color, class: 'form-control' %>
  </td>
  <td>
  <%= f.text_field :price, class: 'form-control' %>
  </td>
  <td>
  <%= f.text_field :note, class: 'form-control' %>
  </td>
</tr>
<% end %>
</tbody>
</table>
<div class="text-center">
<%= fb.submit '一括登録', class: 'btn btn-primary' %>
<%= link_to "戻る", root_path, class: 'btn btn-success' %>
</div>
</div>
<% end %>

<% if model.errors.any? %>
<div class="error-alert">
  <ul>
    <% model.errors.full_messages.each do |message| %>
    <li class='error-message'><%= message %></li>
    <% end %>
  </ul>
</div>
<% end %>