Rails fields_for not creating associated record

In my Rails project, I am creating a Tutorial with an associated Video. When I try to submit this form, in my rails console I keep getting a ROLLBACK as shown below. Can anyone explain to my why it won't save to the database?

My form:

<h2>New Tutorial</h2>
<%= form_for [:admin, @tutorial] do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title, class: "block col-4 field" %>
  <%= f.label :description %>
  <%= f.text_area :description, class: "block col-4 field"  %>
  <%= f.label :thumbnail %>
  <%= f.text_field :thumbnail, class: "block col-4 field"  %>

  <h3>Videos</h3>

  <%= f.fields_for :videos do |builder| %>
    <%= builder.label :title %>
    <%= builder.text_field :title, class: "block col-4 field" %>
     <%= builder.label :description %>
    <%= builder.text_field :description, class: "block col-4 field" %>
    <%= builder.label :thumbnail %>
    <%= builder.text_field :thumbnail, class: "block col-4 field" %>
    <%= builder.label :video_id  %>
    <%= builder.text_field :video_id, class: "block col-4 field" %>
     <%= builder.label :position %>
    <%= builder.text_field :position, class: "block col-4 field" %>
  <% end %>

  <%= f.submit "Save", class: "mt2 btn btn-primary mb1 bg-teal"  %>
<% end %>

My controller:

 class Admin::TutorialsController < Admin::BaseController

  def new
    @tutorial = Tutorial.new
    @tutorial.videos.build
  end

  def create
    @tutorial = Tutorial.new(tutorial_params)
    if @tutorial.save
      flash[:success] = "Successfully created tutorial!"
      redirect_to tutorial_path(@tutorial)
    else
      render :new
    end
  end

  def edit
    @tutorial = Tutorial.find(params[:id])
  end

  def update
    tutorial = Tutorial.find(params[:id])
    if tutorial.update(tutorial_params)
      flash[:success] = "#{tutorial.title} tagged!"
    end
    redirect_to edit_admin_tutorial_path(tutorial)
  end

  private
  def tutorial_params
    params.require(:tutorial).permit(:title, :description, :thumbnail, videos_attributes: [:title, :description, :video_id, :thumbnail, :position])
  end
end

My tutorial model:

class Tutorial < ApplicationRecord
  has_many :videos, ->  { order(position: :ASC) }, dependent: :destroy
  acts_as_taggable_on :tags, :tag_list
  accepts_nested_attributes_for :videos

  scope :without_classroom, -> { where(classroom: false) }
end

And my video model:

class Video < ApplicationRecord
  has_many :user_videos
  has_many :users, through: :user_videos
  belongs_to :tutorial

  validates_presence_of :position 
end

And my rails console log:

Started POST "/admin/tutorials" for 127.0.0.1 at 2019-02-07 10:11:18 -0700
Processing by Admin::TutorialsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"mVD5oCSIAtsTZ86ksWFw4DEpSu2YS89333PK19fhGuck7HMuyoNs3eCulOX2SpX/IPvcPdywMxSxNoa9Q0cu9g==", "tutorial"=>{"title"=>"Sweet nothing", "description"=>"I am here", "thumbnail"=>"www.google.com", "videos_attributes"=>{"0"=>{"title"=>"This thing", "description"=>"Here we are", "thumbnail"=>"kldsfjdsk", "video_id"=>"6", "position"=>"7"}}}, "commit"=>"Save"}
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  ↳ app/controllers/application_controller.rb:8
   (0.2ms)  BEGIN
  ↳ app/controllers/admin/tutorials_controller.rb:10
   (0.2ms)  ROLLBACK
  ↳ app/controllers/admin/tutorials_controller.rb:10
  Rendering admin/tutorials/new.html.erb within layouts/application
  Rendered admin/tutorials/new.html.erb within layouts/application (4.1ms)
  Rendered partials/_nav.html.erb (1.9ms)
Completed 200 OK in 93ms (Views: 28.7ms | ActiveRecord: 13.7ms)