diff --git a/cura/Machines/VariantNode.py b/cura/Machines/VariantNode.py
index fa0c61bd3d..27e359afb1 100644
--- a/cura/Machines/VariantNode.py
+++ b/cura/Machines/VariantNode.py
@@ -84,7 +84,7 @@ class VariantNode(ContainerNode):
                 return material_node
         # First fallback: Choose any material with matching diameter.
         for material_node in self.materials.values():
-            if approximate_diameter == int(material_node.getMetaDataEntry("approximate_diameter")):
+            if material_node.getMetaDataEntry("approximate_diameter") and approximate_diameter == int(material_node.getMetaDataEntry("approximate_diameter")):
                 return material_node
         fallback = next(iter(self.materials.values()))  # Should only happen with empty material node.
         Logger.log("w", "Could not find preferred material {preferred_material} with diameter {diameter} for variant {variant_id}, falling back to {fallback}.".format(
diff --git a/cura/Settings/MachineManager.py b/cura/Settings/MachineManager.py
index b62b3516f6..3fb55c0e70 100755
--- a/cura/Settings/MachineManager.py
+++ b/cura/Settings/MachineManager.py
@@ -619,7 +619,10 @@ class MachineManager(QObject):
         global_container_stack = cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack()
         if not global_container_stack:
             return False
-        return self.activeQualityGroup().is_experimental
+        active_quality_group = self.activeQualityGroup()
+        if active_quality_group is None:
+            return False
+        return active_quality_group.is_experimental
 
     @pyqtProperty(str, notify = activeIntentChanged)
     def activeIntentCategory(self) -> str:
@@ -1431,6 +1434,8 @@ class MachineManager(QObject):
                 else:
                     machine_node = ContainerTree.getInstance().machines.get(self._global_container_stack.definition.getId())
                     variant_node = machine_node.variants.get(extruder_configuration.hotendID)
+                    if variant_node is None:
+                        continue
                     self._setVariantNode(position, variant_node)
 
                     # Find the material profile that the printer has stored.
diff --git a/plugins/XmlMaterialProfile/XmlMaterialProfile.py b/plugins/XmlMaterialProfile/XmlMaterialProfile.py
index 7dfa6483d2..fe0f73f2b3 100644
--- a/plugins/XmlMaterialProfile/XmlMaterialProfile.py
+++ b/plugins/XmlMaterialProfile/XmlMaterialProfile.py
@@ -87,7 +87,6 @@ class XmlMaterialProfile(InstanceContainer):
                 container.metaDataChanged.emit(container)
             for k, v in new_setting_values_dict.items():
                 self.setProperty(k, "value", v)
-            return
 
     ##  Overridden from InstanceContainer, similar to setMetaDataEntry.
     #   without this function the setName would only set the name of the specific nozzle / material / machine combination container