diff --git a/app/assets/javascripts/protocols/steps.js.erb b/app/assets/javascripts/protocols/steps.js.erb
index 93ca6d6b2..c9e74e682 100644
--- a/app/assets/javascripts/protocols/steps.js.erb
+++ b/app/assets/javascripts/protocols/steps.js.erb
@@ -593,21 +593,15 @@
           animateSpinner(null, false);
           setupAssetsLoading();
         },
-        error: function(e) {
-          $form.after(xhr.responseJSON.html);
-          var $new_form = $form.next();
-          $form.remove();
-
-          $errInput = $new_form.find(".form-group.has-error")
-                               .first()
-                               .find("input");
-          renderFormError(e, $errInput);
-
-          formCallback($form);
-          applyCancelOnNew();
+        error: function(xhr) {
+          if (xhr.responseJSON['assets.file'] != null) {
+            $('#new-step-assets-group').addClass('has-error');
+            $('#new-step-assets-tab').addClass('has-error');
+            $.each(xhr.responseJSON['assets.file'], function(_, value) {
+               $('#new-step-assets-group').prepend('<span class="help-block">' + value + '</span>');
+            });
+          }
           animateSpinner(null, false);
-
-          TinyMCE.destroyAll();
           SmartAnnotation.preventPropagation('.atwho-user-popover');
         }
       });
diff --git a/app/assets/javascripts/sitewide/drag_n_drop.js.erb b/app/assets/javascripts/sitewide/drag_n_drop.js.erb
index f585c3aaa..bb79294c2 100644
--- a/app/assets/javascripts/sitewide/drag_n_drop.js.erb
+++ b/app/assets/javascripts/sitewide/drag_n_drop.js.erb
@@ -26,7 +26,7 @@
       $('.panel-step-attachment-new').remove();
       _dragNdropAssetsOff();
       for(var i = 0; i < droppedFiles.length; i++) {
-        $('#new-step-assets')
+        $('#new-step-assets-group')
           .append(_uploadedAssetPreview(droppedFiles[i], i))
           .promise()
           .done(function() {
@@ -49,7 +49,6 @@
         var name = 'step[assets_attributes][' + index + '][file]';
         fd.append(name, droppedFiles[i]);
       }
-      droppedFiles = [];
       filesValid = true;
       totalSize = 0;
       _dragNdropAssetsOff();
diff --git a/app/controllers/steps_controller.rb b/app/controllers/steps_controller.rb
index 9b12b30b6..d64dfe1ac 100644
--- a/app/controllers/steps_controller.rb
+++ b/app/controllers/steps_controller.rb
@@ -96,11 +96,9 @@ class StepsController < ApplicationController
           status: :ok
         end
       else
-        format.json {
-          render json: {
-            html: render_to_string(partial: 'new.html.erb')
-          }, status: :bad_request
-        }
+        format.json do
+          render json: @step.errors.to_json, status: :bad_request
+        end
       end
     end
   end
diff --git a/app/views/steps/_empty_step.html.erb b/app/views/steps/_empty_step.html.erb
index 1882f419b..67f048b13 100644
--- a/app/views/steps/_empty_step.html.erb
+++ b/app/views/steps/_empty_step.html.erb
@@ -50,9 +50,11 @@
                style="display: none" multiple>
       </label>
     </div>
-    <%= f.nested_fields_for :assets do |ff| %>
-      <%= render "form_assets.html.erb", ff: ff, step: step %>
-    <% end %>
+    <div id="new-step-assets-group" class="form-group">
+      <%= f.nested_fields_for :assets do |ff| %>
+        <%= render "form_assets.html.erb", ff: ff, step: step %>
+      <% end %>
+    </div>
   </div>
   <div class="tab-pane" role="tabpanel" id="new-step-tables">
     <%= f.nested_fields_for :tables do |ff| %>
diff --git a/config/initializers/paperclip.rb b/config/initializers/paperclip.rb
index a1ecb31c0..e95a80c6f 100644
--- a/config/initializers/paperclip.rb
+++ b/config/initializers/paperclip.rb
@@ -217,6 +217,7 @@ module Paperclip
           application/vnd.sun.xml.calc.template
           application/vnd.stardivision.calc
           application/x-starcalc
+          application/CDFV2-encrypted
         )) ||
         # Presentation application
         (Set[content_type, content_types_from_name].subset? Set.new %w(