Add our own JSON handling actions for update and delete. Spree no longer does this for us.

app/controllers/spree/admin/line_items_controller_decorator.rb

@@ -34,6 +34,27 @@ Spree::Admin::LineItemsController.class_eval do
     end
   end
 
+  def update
+    respond_to do |format|
+      format.html { render_order_form }
+      format.json {
+        if @line_item.update_attributes(params[:line_item])
+          render nothing: true, status: 204 # No Content, does not trigger ng resource auto-update
+        else
+          render json: {errors: @line_item.errors}, status: 412
+        end
+      }
+    end
+  end
+
+  def destroy
+    @line_item.destroy
+
+    respond_to do |format|
+      format.html { render_order_form }
+      format.json { render nothing: true, status: 204 } # No Content
+    end
+  end
 
   private