diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 7ee83c03cb4092390f330e8b4c6ef9946fb54e36..9cd65d75f03330c095cef67357fe3a1004b29d76 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -26,6 +26,12 @@ class ApplicationController < ActionController::API
   # tracking user in papertrail
   before_action :set_paper_trail_whodunnit
 
+  rescue_from Exception do |exception|
+    logger.fatal exception
+    logger.fatal exception.backtrace.first(5).join("\n")
+    render status: :internal_server_error
+  end
+
   # check if client application is allowed to consumes the API.
   before_action :allow_client_application, if: -> { Feature.active?(:allow_client_application) }
 
diff --git a/app/controllers/v1/learning_objects_controller.rb b/app/controllers/v1/learning_objects_controller.rb
index bfed4f10705d4dac7e5f2ec4342f434a8a0a086a..f7c0ed1b990d70e5d3da70b38c9f2b4c2f94d2b3 100644
--- a/app/controllers/v1/learning_objects_controller.rb
+++ b/app/controllers/v1/learning_objects_controller.rb
@@ -74,10 +74,17 @@ class V1::LearningObjectsController < ApplicationController
   # PATCH/PUT /learning_objects/1
   # PATCH/PUT /learning_objects/1.json
   def update
-    if !learning_object_params[:object_type_id].blank? && learning_object_params[:object_type_id] != @learning_object.object_type_id && learning_object_params[:link].blank?
+    lo_params = learning_object_params
+    if !lo_params[:object_type_id].blank? && lo_params[:object_type_id] != @learning_object.object_type_id && lo_params[:link].blank?
       change_object_type_id = true
     end
-    if @learning_object.update(learning_object_params)
+
+    if lo_params[:thumbnail] == "null"
+      @learning_object.thumbnail.clear
+      lo_params.delete(:thumbnail)
+    end
+
+    if @learning_object.update(lo_params)
       update_learning_object_associations(@learning_object, change_object_type_id)
       publisher = LearningObjectPublisher.new(DspaceService.create_client)
       publisher.update_dspace(@learning_object)