diff --git a/dist/ladb_opencutlist-dev.rbz b/dist/ladb_opencutlist-dev.rbz
index 9a62845fc..9925dde1f 100644
Binary files a/dist/ladb_opencutlist-dev.rbz and b/dist/ladb_opencutlist-dev.rbz differ
diff --git a/src/ladb_opencutlist/js/plugins/jquery.ladb.dialog.js b/src/ladb_opencutlist/js/plugins/jquery.ladb.dialog.js
index 414f2dfb8..d66b8bae5 100644
--- a/src/ladb_opencutlist/js/plugins/jquery.ladb.dialog.js
+++ b/src/ladb_opencutlist/js/plugins/jquery.ladb.dialog.js
@@ -246,6 +246,14 @@
         return n;
     };
 
+    LadbDialog.prototype.notifyErrors = function(errors) {
+        if (Array.isArray(errors)) {
+            for (var i = 0; i < errors.length; i++) {
+                this.notify('<i class="ladb-opencutlist-icon-warning"></i> ' + i18next.t(errors[i]), 'error');
+            }
+        }
+    };
+
     LadbDialog.prototype.setupTooltips = function() {
         $('[data-toggle="tooltip"]').tooltip({
             container: 'body'
diff --git a/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-cutlist.js b/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-cutlist.js
index 6475a5d89..044cd6820 100644
--- a/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-cutlist.js
+++ b/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-cutlist.js
@@ -344,12 +344,10 @@
 
             rubyCallCommand('cutlist_part_highlight', part, function (response) {
 
-                var success = response['success'];
-
-                if (success) {
-                    that.opencutlist.minimize();
-                } else {
+                if (response['errors']) {
                     that.opencutlist.notify('<i class="ladb-opencutlist-icon-warning"></i> ' + i18next.t('tab.cutlist.highlight_error', {'name': part.name}), 'error');
+                } else {
+                    that.opencutlist.minimize();
                 }
 
             });
@@ -414,10 +412,30 @@
                     that.editedPart.cumulable = $selectCumulable.val();
                     that.editedPart.orientation_locked_on_axis = $inputOrientationLockedOnAxis.is(':checked');
 
-                    rubyCallCommand('cutlist_part_update', that.editedPart, function() {
+                    rubyCallCommand('cutlist_part_update', that.editedPart, function(response) {
+
+                        if (response['errors']) {
+
+                            that.opencutlist.notifyErrors(response['errors']);
+
+                        } else {
+
+                            var partId = that.editedPart.id;
+                            var wTop = $('#ladb_part_' + partId).offset().top - $(window).scrollTop();
+
+                            // Refresh the list
+                            that.generateCutlist(function() {
+
+                                // Try to scroll to the edited part's row
+                                var $part = $('#ladb_part_' + partId);
+                                if ($part.length > 0) {
+                                    $part.effect("highlight", {}, 1500);
+                                    $('html, body').animate({ scrollTop: $part.offset().top - wTop }, 0);
+                                }
+
+                            });
 
-                        var partId = that.editedPart.id;
-                        var wTop = $('#ladb_part_' + partId).offset().top - $(window).scrollTop();
+                        }
 
                         // Reset edited part
                         that.editedPart = null;
@@ -425,18 +443,6 @@
                         // Hide modal
                         $modal.modal('hide');
 
-                        // Refresh the list
-                        that.generateCutlist(function() {
-
-                            // Try to scroll to the edited part's row
-                            var $part = $('#ladb_part_' + partId);
-                            if ($part.length > 0) {
-                                $part.effect("highlight", {}, 1500);
-                                $('html, body').animate({ scrollTop: $part.offset().top - wTop }, 0);
-                            }
-
-                        });
-
                     });
 
                 });
@@ -492,7 +498,18 @@
                 // Fetch form values
                 that.editedGroup.material_name = $selectMaterialName.val();
 
-                rubyCallCommand('cutlist_group_update', that.editedGroup, function() {
+                rubyCallCommand('cutlist_group_update', that.editedGroup, function(response) {
+
+                    if (response['errors']) {
+
+                        that.opencutlist.notifyErrors(response['errors']);
+
+                    } else {
+
+                        // Refresh the list
+                        that.generateCutlist();
+
+                    }
 
                     // Reset edited group
                     that.editedGroup = null;
@@ -500,9 +517,6 @@
                     // Hide modal
                     $modal.modal('hide');
 
-                    // Refresh the list
-                    that.generateCutlist();
-
                 });
 
             });
diff --git a/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-materials.js b/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-materials.js
index 465e12f79..e024da4ce 100644
--- a/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-materials.js
+++ b/src/ladb_opencutlist/js/plugins/jquery.ladb.tab-materials.js
@@ -73,7 +73,7 @@
             }));
 
             // Update items state
-            that.$itemPurgeUnused.closest('li').toggleClass('disabled', materials.length == 0);
+            that.$itemPurgeUnused.closest('li').toggleClass('disabled', materials == null || materials.length == 0);
 
             // Update page
             that.$page.empty();
@@ -416,7 +416,18 @@
                 // Flag to ignore next material change event
                 that.ignoreNextMaterialChangeEvent = true;
 
-                rubyCallCommand('materials_update', that.editedMaterial, function() {
+                rubyCallCommand('materials_update', that.editedMaterial, function(response) {
+
+                    if (response['errors']) {
+
+                        that.opencutlist.notifyErrors(response['errors']);
+
+                    } else {
+
+                        // Refresh the list
+                        that.loadList();
+
+                    }
 
                     // Reset edited material
                     that.editedMaterial = null;
@@ -424,9 +435,6 @@
                     // Hide modal
                     $modal.modal('hide');
 
-                    // Refresh the list
-                    that.loadList();
-
                 });
 
             });
diff --git a/src/ladb_opencutlist/ruby/controller/cutlist_controller.rb b/src/ladb_opencutlist/ruby/controller/cutlist_controller.rb
index a816454e6..fde6484ba 100644
--- a/src/ladb_opencutlist/ruby/controller/cutlist_controller.rb
+++ b/src/ladb_opencutlist/ruby/controller/cutlist_controller.rb
@@ -356,17 +356,17 @@ def _get_inherited_material(path)
       if @instance_infos_cache.length == 0
         if model
           if entities.length == 0
-            cutlist_def.add_error("tab.cutlist.error.no_entities")
+            cutlist_def.add_error('tab.cutlist.error.no_entities')
             else
               if use_selection
-              cutlist_def.add_error("tab.cutlist.error.no_component_in_selection")
+              cutlist_def.add_error('tab.cutlist.error.no_component_in_selection')
             else
-              cutlist_def.add_error("tab.cutlist.error.no_component_in_model")
+              cutlist_def.add_error('tab.cutlist.error.no_component_in_model')
             end
-            cutlist_def.add_tip("tab.cutlist.tip.no_component")
+            cutlist_def.add_tip('tab.cutlist.tip.no_component')
           end
         else
-          cutlist_def.add_error("tab.cutlist.error.no_model")
+          cutlist_def.add_error('tab.cutlist.error.no_model')
         end
       end
 
@@ -819,7 +819,7 @@ def numbers_command(settings, reset)
         group_id = settings['group_id']
 
         model = Sketchup.active_model
-        definitions = model.definitions
+        definitions = model ? model.definitions : []
 
         @cutlist[:groups].each { |group|
 
@@ -849,10 +849,12 @@ def part_get_thumbnail_command(part_data)
           :thumbnail_file => ''
       }
 
+      model = Sketchup.active_model
+      return response unless model
+
       # Extract parameters
       definition_id = part_data['definition_id']
 
-      model = Sketchup.active_model
       definitions = model.definitions
       definition = definitions[definition_id]
       if definition
@@ -876,13 +878,8 @@ def part_get_thumbnail_command(part_data)
 
     def part_highlight_command(part_data)
 
-      response = {
-          :success => false
-      }
-
       model = Sketchup.active_model
-
-      return response unless model
+      return { :errors => [ 'tab.cutlist.error.no_model' ] } unless model
 
       # Extract parameters
       name = part_data['name']
@@ -892,7 +889,6 @@ def part_highlight_command(part_data)
       material_name = part_data['material_name']
       entity_serialized_paths = part_data['entity_serialized_paths']
 
-
       # Populate instance defs
       entity_infos = []
       entity_serialized_paths.each { |entity_serialized_path|
@@ -914,15 +910,15 @@ def part_highlight_command(part_data)
         highlight_tool = HighlightPartTool.new(text_line_1, text_line_2, entity_infos)
         model.select_tool(highlight_tool)
 
-        response[:success] = true
-
       end
 
-      response
     end
 
     def part_update_command(part_data)
 
+      model = Sketchup.active_model
+      return { :errors => [ 'tab.cutlist.error.no_model' ] } unless model
+
       # Extract parameters
       definition_id = part_data['definition_id']
       name = part_data['name']
@@ -931,36 +927,40 @@ def part_update_command(part_data)
       orientation_locked_on_axis = part_data['orientation_locked_on_axis']
       entity_ids = part_data['entity_ids']
 
-      model = Sketchup.active_model
-
-      # Update definition's name
       definitions = model.definitions
       definition = definitions[definition_id]
-      if definition and definition.name != name
-        definition.name = name
-      end
 
-      definition_attributes = DefinitionAttributes.new(definition)
-      if cumulable != definition_attributes.cumulable or orientation_locked_on_axis != definition_attributes.orientation_locked_on_axis
-        definition_attributes.cumulable = cumulable
-        definition_attributes.orientation_locked_on_axis = orientation_locked_on_axis
-        definition_attributes.write_to_attributes
-      end
+      if definition
 
-      # Update component instance material
-      materials = model.materials
-      if material_name.nil? or material_name.empty? or (material = materials[material_name])
+        # Update definition's name
+        if definition.name != name
+          definition.name = name
+        end
+
+        # Update definition's attributes
+        definition_attributes = DefinitionAttributes.new(definition)
+        if cumulable != definition_attributes.cumulable or orientation_locked_on_axis != definition_attributes.orientation_locked_on_axis
+          definition_attributes.cumulable = cumulable
+          definition_attributes.orientation_locked_on_axis = orientation_locked_on_axis
+          definition_attributes.write_to_attributes
+        end
+
+        # Update component instance material
+        materials = model.materials
+        if material_name.nil? or material_name.empty? or (material = materials[material_name])
 
-        entity_ids.each { |entity_id|
-          entity = ModelUtils::find_entity_by_id(model, entity_id)
-          if entity
-            if material_name.nil? or material_name.empty?
-              entity.material = nil
-            elsif entity.material != material
-              entity.material = material
+          entity_ids.each { |entity_id|
+            entity = ModelUtils::find_entity_by_id(model, entity_id)
+            if entity
+              if material_name.nil? or material_name.empty?
+                entity.material = nil
+              elsif entity.material != material
+                entity.material = material
+              end
             end
-          end
-        }
+          }
+
+        end
 
       end
 
@@ -968,15 +968,16 @@ def part_update_command(part_data)
 
     def group_update_command(group_data)
 
+      model = Sketchup.active_model
+      return { :errors => [ 'tab.cutlist.error.no_model' ] } unless model
+
       # Extract parameters
-      id = group_data['id']
       material_name = group_data['material_name']
       parts = group_data['parts']
 
-      model = Sketchup.active_model
+      materials = model.materials
 
       # Update component instance material
-      materials = model.materials
       if material_name.nil? or material_name.empty? or (material = materials[material_name])
 
         parts.each { |part_data|
diff --git a/src/ladb_opencutlist/ruby/controller/materials_controller.rb b/src/ladb_opencutlist/ruby/controller/materials_controller.rb
index 7e934becd..f654b3de2 100644
--- a/src/ladb_opencutlist/ruby/controller/materials_controller.rb
+++ b/src/ladb_opencutlist/ruby/controller/materials_controller.rb
@@ -102,7 +102,7 @@ def list_command()
           response[:errors].push('tab.materials.error.no_materials')
         end
       else
-        response[:errors].push("tab.materials.error.no_model")
+        response[:errors].push('tab.materials.error.no_model')
       end
 
       # Sort materials by type ASC, display_name ASC
@@ -113,13 +113,19 @@ def list_command()
 
     def purge_unused_command()
 
-      materials = Sketchup.active_model.materials
+      model = Sketchup.active_model
+      return { :errors => [ 'tab.materials.error.no_model' ] } unless model
+
+      materials = model.materials
       materials.purge_unused
 
     end
 
     def update_command(material_data)
 
+      model = Sketchup.active_model
+      return { :errors => [ 'tab.materials.error.no_model' ] } unless model
+
       name = material_data['name']
       display_name = material_data['display_name']
       attributes = material_data['attributes']
@@ -131,7 +137,6 @@ def update_command(material_data)
       std_sections = attributes['std_sections']
 
       # Fetch material
-      model = Sketchup.active_model
       materials = model.materials
       material = materials[name]
 
@@ -158,18 +163,19 @@ def update_command(material_data)
 
     def remove_command(material_data)
 
+      model = Sketchup.active_model
+      return { :errors => [ 'tab.materials.error.no_model' ] } unless model
+
       name = material_data['name']
-      display_name = material_data['display_name']
+
+      response = {
+          :errors => []
+      }
 
       # Fetch material
-      model = Sketchup.active_model
       materials = model.materials
       material = materials[name]
 
-      response = {
-          :errors => [],
-      }
-
       if material
 
         begin
@@ -178,6 +184,8 @@ def remove_command(material_data)
           response[:errors].push('tab.materials.error.failed_removing_material')
         end
 
+      else
+        response[:errors].push('tab.materials.error.failed_removing_material')
       end
 
       response
@@ -185,17 +193,20 @@ def remove_command(material_data)
 
     def import_from_skm_command
 
-      # Fetch material
       model = Sketchup.active_model
-      materials = model.materials
+      return { :errors => [ 'tab.materials.error.no_model' ] } unless model
 
       response = {
-          :errors => [],
+          :errors => []
       }
 
-      dir, filename = File.split(model ? model.path : '')
+      # Fetch material
+      materials = model.materials
+
+      dir, filename = File.split(model.path)
       path = UI.openpanel(Plugin.get_i18n_string('tab.materials.import_from_skm.title'), dir, "Material Files|*.skm;||")
       if path
+
         begin
           materials.load(path)
         rescue
@@ -209,31 +220,31 @@ def import_from_skm_command
 
     def export_to_skm_command(material_data)
 
+      model = Sketchup.active_model
+      return { :errors => [ 'tab.materials.error.no_model' ] } unless model
+
       name = material_data['name']
       display_name = material_data['display_name']
 
       # Fetch material
-      model = Sketchup.active_model
       materials = model.materials
       material = materials[name]
 
-      response = {
-          :errors => [],
-      }
-
       if material
 
-        dir, filename = File.split(model ? model.path : '')
+        dir, filename = File.split(model.path)
         path = UI.savepanel(Plugin.get_i18n_string('tab.materials.export_to_skm.title'), dir, display_name + '.skm')
         if path
           begin
             material.save_as(path)
-            response[:export_path] = path;
+            response[:export_path] = path
           rescue
             response[:errors].push('tab.materials.error.failed_export_skm_file')
           end
         end
 
+      else
+        response[:errors].push('tab.materials.error.failed_export_skm_file')
       end
 
       response
diff --git a/src/ladb_opencutlist/ruby/plugin.rb b/src/ladb_opencutlist/ruby/plugin.rb
index 266728dbe..ab51cd14a 100644
--- a/src/ladb_opencutlist/ruby/plugin.rb
+++ b/src/ladb_opencutlist/ruby/plugin.rb
@@ -13,7 +13,7 @@ class Plugin
 
     NAME = 'OpenCutList'.freeze
     VERSION = '1.4.1-dev'.freeze
-    BUILD = '201804061110'.freeze
+    BUILD = '201804091154'.freeze
 
     DEFAULT_SECTION = ATTRIBUTE_DICTIONARY = 'ladb_opencutlist'.freeze
     BC_DEFAULT_SECTION = BC_ATTRIBUTE_DICTIONARY = 'ladb_toolbox'.freeze