cocoon: form error messages not returning with `remote: true` when creating pictures?

Hi Nathan. I am getting similar to this issue https://github.com/nathanvda/cocoon/issues/150 where I use remotipart gem to get past the authenticity token issue when using remote: true in a form. When I use remote: true everything renders out correctly from server to the page except error messages are not being sent. The only reason I believe its a cocoon issue is the problem only occurs when I add pictures. If I do not add any pictures and submit a invalid form the error messages display.My server reads these two results

POST req without pics

Started POST “/users/2/galleries” for ::1 at 2017-12-11 16:52:42 +1100 Processing by GalleriesController#create as JS Parameters: {“utf8”=>“✓”, “gallery”=>{“name”=>“Hello”, “cover”=>“”}, “commit”=>“Create Gallery”, “user_id”=>“2”} User Load (0.0ms) SELECT “users”.* FROM “users” WHERE “users”.“id” = ? LIMIT ? [[“id”, 2], [“LIMIT”, 1]] (0.0ms) begin transaction User Load (0.5ms) SELECT “users”.* FROM “users” WHERE “users”.“id” = ? LIMIT ? [[“id”, 2], [“LIMIT”, 1]] (0.0ms) rollback transaction Rendering galleries/new.js.erb Rendering galleries/new.html.erb Rendered shared/_error_messages.html.erb (0.5ms) Rendered galleries/_picture_fields.html.erb (1.0ms) Rendered galleries/_form.html.erb (303.9ms) Rendered galleries/new.html.erb (455.6ms) Rendered galleries/new.js.erb (605.8ms) Completed 200 OK in 796ms (Views: 791.3ms | ActiveRecord: 0.5ms)

POST req with pics

Started POST “/users/2/galleries” for ::1 at 2017-12-11 16:52:11 +1100 Processing by GalleriesController#create as JS Parameters: {“utf8”=>“✓”, “gallery”=>{“name”=>“Hello”, “cover”=>“”, “pictures_attributes”=>{“1512971529011”=>{“picture_cache”=>“”, “_destroy”=>“false”, “picture”=>#<ActionDispatch::Http::UploadedFile:0xd1409f0 @tempfile=#Tempfile:C:/Users/Lee/AppData/Local/Temp/RackMultipart20171211-11944-1ox30j6.jpg, @original_filename=“All-Out-EDM-mix-picture-3.jpg”, @content_type=“image/jpeg”, @headers=“Content-Disposition: form-data; name="gallery[pictures_attributes][1512971529011][picture]"; filename="All-Out-EDM-mix-picture-3.jpg"\r\nContent-Type: image/jpeg\r\n”>}}}, “commit”=>“Create Gallery”, “remotipart_submitted”=>“true”, “authenticity_token”=>“6H0jpCI/uTwUTeKMdWK3ttYL2loFFjSZh8DXoDdxhPrPUL8YNVLQL05/V9iMVidAmoeN+An+8D1+39q77IQQIQ==”, “X-Requested-With”=>“IFrame”, “X-Http-Accept”=>“text/javascript, application/javascript, application/ecmascript, application/x-ecmascript, /; q=0.01”, “user_id”=>“2”} User Load (0.0ms) SELECT “users”.* FROM “users” WHERE “users”.“id” = ? LIMIT ? [[“id”, 2], [“LIMIT”, 1]] (0.0ms) begin transaction User Load (0.0ms) SELECT “users”.* FROM “users” WHERE “users”.“id” = ? LIMIT ? [[“id”, 2], [“LIMIT”, 1]] (0.5ms) rollback transaction Rendering galleries/new.js.erb Rendering galleries/new.html.erb Rendered shared/_error_messages.html.erb (0.5ms) Rendered galleries/_picture_fields.html.erb (2.0ms) Rendered galleries/_picture_fields.html.erb (1.0ms) Rendered galleries/_form.html.erb (490.6ms) Rendered galleries/new.html.erb (663.8ms) Rendered galleries/new.js.erb (828.0ms) Completed 200 OK in 1521ms (Views: 1026.6ms | ActiveRecord: 0.5ms)

The form looks like this

<%= form_for([@user, @gallery], remote: true) do |f| %>
<%= render 'shared/error_messages', object: f.object %>
  <div class="field">
    <%= f.label :name %>
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :cover %>
    <%= f.text_field :cover %>
  </div>
  <table class="user-picture-form">
    <tbody>
      <%= f.fields_for :pictures do |pic| %>
      <%= render 'picture_fields', f: pic %>
      <% end %>
   </tbody>
 </table>
 <div class="links">
   <%= link_to_add_association 'add picture', f, :pictures %>
   <%= f.submit %>
 </div>
<% end %>

and

<tr class="nested-fields">
  <td>
    <%= f.file_field :picture, accept: 'image/jpg,image/jpeg,image/gif,image/png' %>
    <%= f.hidden_field :picture_cache, :value => f.object.picture_cache %>
  </td>
  <td class="thumb">
    <% if f.object.picture.url.present? %>
    <%= image_tag f.object.picture.url %>
    <% end %>
    </td>
    <td> 
      <%= link_to_remove_association "remove", f %>
    </td>
</tr>

Also I am confused because removing remote: true from the form and submitting as html and also adding pictures the form returns the errors correctly so things work when the response is HTML. I even removed remotipart gem and changed ActionView::Helpers::FormTagHelper.embed_authenticity_token_in_remote_forms = true to true but then rails would not recognise js format. Wondering if you can shed some light on this.