diff --git a/cura/Machines/MachineNode.py b/cura/Machines/MachineNode.py
index efc5b0f128..ac293a1503 100644
--- a/cura/Machines/MachineNode.py
+++ b/cura/Machines/MachineNode.py
@@ -77,6 +77,9 @@ class MachineNode(ContainerNode):
         # Create the quality group for each available type.
         quality_groups = {}
         for quality_type, global_quality_node in self.global_qualities.items():
+            if not global_quality_node.container:
+                Logger.log("w", "Node {0} doesn't have a container.".format(global_quality_node.container_id))
+                continue
             quality_groups[quality_type] = QualityGroup(name = global_quality_node.container.getMetaDataEntry("name", "Unnamed profile"), quality_type = quality_type)
             quality_groups[quality_type].node_for_global = global_quality_node
             for extruder, qualities_per_type in enumerate(qualities_per_type_per_extruder):
@@ -116,7 +119,7 @@ class MachineNode(ContainerNode):
     def getQualityChangesGroups(self, variant_names: List[str], material_bases: List[str], extruder_enabled: List[bool]) -> List[QualityChangesGroup]:
         machine_quality_changes = ContainerRegistry.getInstance().findContainersMetadata(type = "quality_changes", definition = self.quality_definition)  # All quality changes for each extruder.
 
-        groups_by_name = {}  # Group quality changes profiles by their display name. The display name must be unique for quality changes. This finds profiles that belong together in a group.
+        groups_by_name = {}  #type: Dict[str, QualityChangesGroup]  # Group quality changes profiles by their display name. The display name must be unique for quality changes. This finds profiles that belong together in a group.
         for quality_changes in machine_quality_changes:
             name = quality_changes["name"]
             if name not in groups_by_name:
@@ -143,7 +146,7 @@ class MachineNode(ContainerNode):
     #   quality is taken.
     #   If there are no global qualities, an empty quality is returned.
     def preferredGlobalQuality(self) -> QualityNode:
-        return self.global_qualities.get(self.preferred_quality_type, next(iter(self.global_qualities)))
+        return self.global_qualities.get(self.preferred_quality_type, next(iter(self.global_qualities.values())))
 
     ##  (Re)loads all variants under this printer.
     def _loadAll(self):
diff --git a/cura/Machines/MaterialManager.py b/cura/Machines/MaterialManager.py
index 5d5938d95d..e298ef7389 100644
--- a/cura/Machines/MaterialManager.py
+++ b/cura/Machines/MaterialManager.py
@@ -132,7 +132,7 @@ class MaterialManager(QObject):
         # Fetch the available materials (ContainerNode) for the current active machine and extruder setup.
         materials = self.getAvailableMaterials(machine.definition.getId(), nozzle_name)
         compatible_material_diameter = str(round(extruder_stack.getCompatibleMaterialDiameter()))
-        result = {key: material for key, material in materials.items() if material.container.getMetaDataEntry("approximate_diameter") == compatible_material_diameter}
+        result = {key: material for key, material in materials.items() if material.container and material.container.getMetaDataEntry("approximate_diameter") == compatible_material_diameter}
         return result
 
     #
@@ -268,6 +268,8 @@ class MaterialManager(QObject):
 
     @pyqtSlot("QVariant", str)
     def setMaterialName(self, material_node: "MaterialNode", name: str) -> None:
+        if material_node.container is None:
+            return
         root_material_id = material_node.container.getMetaDataEntry("base_file")
         if root_material_id is None:
             return
@@ -279,6 +281,8 @@ class MaterialManager(QObject):
 
     @pyqtSlot("QVariant")
     def removeMaterial(self, material_node: "MaterialNode") -> None:
+        if material_node.container is None:
+            return
         root_material_id = material_node.container.getMetaDataEntry("base_file")
         if root_material_id is not None:
             self.removeMaterialByRootId(root_material_id)
@@ -343,6 +347,9 @@ class MaterialManager(QObject):
     #
     @pyqtSlot("QVariant", result = str)
     def duplicateMaterial(self, material_node: MaterialNode, new_base_id: Optional[str] = None, new_metadata: Dict[str, Any] = None) -> Optional[str]:
+        if material_node.container is None:
+            Logger.log("e", "Material node {0} doesn't have container.".format(material_node.container_id))
+            return "ERROR"
         root_material_id = cast(str, material_node.container.getMetaDataEntry("base_file", ""))
         return self.duplicateMaterialByRootId(root_material_id, new_base_id, new_metadata)
 
@@ -359,7 +366,11 @@ class MaterialManager(QObject):
         machine_manager = application.getMachineManager()
         extruder_stack = machine_manager.activeStack
 
-        machine_definition = application.getGlobalContainerStack().definition
+        global_stack = application.getGlobalContainerStack()
+        if global_stack is None:
+            Logger.log("e", "Global stack not present!")
+            return "ERROR"
+        machine_definition = global_stack.definition
         root_material_id = machine_definition.getMetaDataEntry("preferred_material", default = "generic_pla")
 
         approximate_diameter = str(extruder_stack.approximateMaterialDiameter)
diff --git a/cura/Machines/Models/BaseMaterialsModel.py b/cura/Machines/Models/BaseMaterialsModel.py
index 81be676a33..0a5e58d52f 100644
--- a/cura/Machines/Models/BaseMaterialsModel.py
+++ b/cura/Machines/Models/BaseMaterialsModel.py
@@ -106,7 +106,10 @@ class BaseMaterialsModel(ListModel):
     def _materialsListChanged(self, material: MaterialNode) -> None:
         if material.variant.container_id != self._extruder_stack.variant.getId():
             return
-        if material.variant.machine.container_id != cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack().definition.getId():
+        global_stack = cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack()
+        if not global_stack:
+            return
+        if material.variant.machine.container_id != global_stack.definition.getId():
             return
         self._update()
 
diff --git a/cura/Machines/QualityChangesGroup.py b/cura/Machines/QualityChangesGroup.py
index f798a18e29..65ebb71f4c 100644
--- a/cura/Machines/QualityChangesGroup.py
+++ b/cura/Machines/QualityChangesGroup.py
@@ -16,7 +16,7 @@ class QualityChangesGroup(QObject):
         self.quality_type = quality_type
         self.intent_category = intent_category
         self.is_available = False
-        self.metadata_for_global = None  # type: Optional[str]
+        self.metadata_for_global = {}    # type: Dict[str, Any]
         self.metadata_per_extruder = {}  # type: Dict[int, Dict[str, Any]]
 
     def __str__(self) -> str:
diff --git a/cura/Machines/QualityGroup.py b/cura/Machines/QualityGroup.py
index a4324e069d..951d3717de 100644
--- a/cura/Machines/QualityGroup.py
+++ b/cura/Machines/QualityGroup.py
@@ -5,6 +5,7 @@ from typing import Dict, Optional, List, Set
 
 from PyQt5.QtCore import QObject, pyqtSlot
 
+from UM.Logger import Logger
 from UM.Util import parseBool
 
 from cura.Machines.ContainerNode import ContainerNode
@@ -60,6 +61,9 @@ class QualityGroup(QObject):
         self.node_for_global = node
 
         # Update is_experimental flag
+        if not node.container:
+            Logger.log("w", "Node {0} doesn't have a container.".format(node.container_id))
+            return
         is_experimental = parseBool(node.container.getMetaDataEntry("is_experimental", False))
         self.is_experimental |= is_experimental
 
@@ -67,5 +71,8 @@ class QualityGroup(QObject):
         self.nodes_for_extruders[position] = node
 
         # Update is_experimental flag
+        if not node.container:
+            Logger.log("w", "Node {0} doesn't have a container.".format(node.container_id))
+            return
         is_experimental = parseBool(node.container.getMetaDataEntry("is_experimental", False))
         self.is_experimental |= is_experimental
diff --git a/cura/Machines/QualityManager.py b/cura/Machines/QualityManager.py
index c03c580197..75c8e89e11 100644
--- a/cura/Machines/QualityManager.py
+++ b/cura/Machines/QualityManager.py
@@ -112,12 +112,10 @@ class QualityManager(QObject):
         # Iterate over all quality_types in the machine node
         quality_group_dict = dict()
         for node in nodes_to_check:
-            if node and node.quality_type_map:
-                for quality_type, quality_node in node.quality_type_map.items():
-                    quality_group = QualityGroup(quality_node.getMetaDataEntry("name", ""), quality_type)
-                    quality_group.setGlobalNode(quality_node)
-                    quality_group_dict[quality_type] = quality_group
-                break
+            if node and node.quality_type:
+                quality_group = QualityGroup(node.getMetaDataEntry("name", ""), node.quality_type)
+                quality_group.setGlobalNode(node)
+                quality_group_dict[node.quality_type] = quality_group
 
         return quality_group_dict
 
diff --git a/cura/Settings/ContainerManager.py b/cura/Settings/ContainerManager.py
index a4c75353f5..d1c25530e3 100644
--- a/cura/Settings/ContainerManager.py
+++ b/cura/Settings/ContainerManager.py
@@ -83,6 +83,9 @@ class ContainerManager(QObject):
     #  Update: In order for QML to use objects and sub objects, those (sub) objects must all be QObject. Is that what we want?
     @pyqtSlot("QVariant", str, str)
     def setContainerMetaDataEntry(self, container_node: "ContainerNode", entry_name: str, entry_value: str) -> bool:
+        if container_node.container is None:
+            Logger.log("w", "Container node {0} doesn't have a container.".format(container_node.container_id))
+            return False
         root_material_id = container_node.container.getMetaDataEntry("base_file", "")
         if cura.CuraApplication.CuraApplication.getInstance().getContainerRegistry().isReadOnly(root_material_id):
             Logger.log("w", "Cannot set metadata of read-only container %s.", root_material_id)
@@ -341,6 +344,9 @@ class ContainerManager(QObject):
     @pyqtSlot("QVariant")
     def unlinkMaterial(self, material_node: "MaterialNode") -> None:
         # Get the material group
+        if material_node.container is None:
+            Logger.log("w", "Material node {0} doesn't have a container.".format(material_node.container_id))
+            return
         material_group = MaterialManager.getInstance().getMaterialGroup(material_node.container.getMetaDataEntry("base_file", ""))
 
         if material_group is None:
diff --git a/cura/Settings/CuraContainerRegistry.py b/cura/Settings/CuraContainerRegistry.py
index 314adeeb54..c288f3c0ce 100644
--- a/cura/Settings/CuraContainerRegistry.py
+++ b/cura/Settings/CuraContainerRegistry.py
@@ -28,6 +28,7 @@ from . import GlobalStack
 
 import cura.CuraApplication
 from cura.Settings.cura_empty_instance_containers import empty_quality_container
+from cura.Machines.ContainerTree import ContainerTree
 from cura.Machines.QualityManager import getMachineDefinitionIDForQualitySearch
 from cura.ReaderWriters.ProfileReader import NoProfileException, ProfileReader
 
@@ -386,8 +387,7 @@ class CuraContainerRegistry(ContainerRegistry):
         # Check to make sure the imported profile actually makes sense in context of the current configuration.
         # This prevents issues where importing a "draft" profile for a machine without "draft" qualities would report as
         # successfully imported but then fail to show up.
-        quality_manager = cura.CuraApplication.CuraApplication.getInstance()._quality_manager
-        quality_group_dict = quality_manager.getQualityGroupsForMachineDefinition(global_stack)
+        quality_group_dict = ContainerTree.getInstance().machines[definition_id]
         # "not_supported" profiles can be imported.
         if quality_type != empty_quality_container.getMetaDataEntry("quality_type") and quality_type not in quality_group_dict:
             return catalog.i18nc("@info:status", "Could not find a quality type {0} for the current configuration.", quality_type)
diff --git a/cura/Settings/MachineManager.py b/cura/Settings/MachineManager.py
index 3447581bca..5ad1c2dc43 100755
--- a/cura/Settings/MachineManager.py
+++ b/cura/Settings/MachineManager.py
@@ -24,6 +24,7 @@ from UM.Signal import postponeSignals, CompressTechnique
 
 import cura.CuraApplication  # Imported like this to prevent circular references.
 
+from cura.Machines.ContainerNode import ContainerNode
 from cura.Machines.ContainerTree import ContainerTree
 from cura.Machines.QualityManager import getMachineDefinitionIDForQualitySearch, QualityManager
 from cura.Machines.MaterialManager import MaterialManager
@@ -1185,7 +1186,7 @@ class MachineManager(QObject):
     def _setMaterial(self, position: str, material_node: Optional["MaterialNode"] = None) -> None:
         if self._global_container_stack is None:
             return
-        if material_node:
+        if material_node and material_node.container:
             material_container = material_node.container
             self._global_container_stack.extruders[position].material = material_container
             root_material_id = material_container.getMetaDataEntry("base_file", None)
@@ -1239,6 +1240,9 @@ class MachineManager(QObject):
         # The current quality type is not available so we use the preferred quality type if it's available,
         # otherwise use one of the available quality types.
         quality_type = sorted(list(available_quality_types))[0]
+        if self._global_container_stack is None:
+            Logger.log("e", "Global stack not present!")
+            return
         preferred_quality_type = self._global_container_stack.getMetaDataEntry("preferred_quality_type")
         if preferred_quality_type in available_quality_types:
             quality_type = preferred_quality_type
@@ -1549,7 +1553,7 @@ class MachineManager(QObject):
     @pyqtProperty(bool, notify = activeQualityGroupChanged)
     def hasNotSupportedQuality(self) -> bool:
         global_container_stack = cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack()
-        return global_container_stack and global_container_stack.quality == empty_quality_container and global_container_stack.qualityChanges == empty_quality_changes_container
+        return (not global_container_stack is None) and global_container_stack.quality == empty_quality_container and global_container_stack.qualityChanges == empty_quality_changes_container
 
     def _updateUponMaterialMetadataChange(self) -> None:
         if self._global_container_stack is None:
diff --git a/tests/TestQualityManager.py b/tests/TestQualityManager.py
index 4a0f29c9ee..52c3da4fbb 100644
--- a/tests/TestQualityManager.py
+++ b/tests/TestQualityManager.py
@@ -50,13 +50,6 @@ def test_getQualityGroups(quality_mocked_application):
     assert "normal" in manager.getQualityGroups(mocked_stack)
 
 
-def test_getQualityGroupsForMachineDefinition(quality_mocked_application):
-    manager = QualityManager(quality_mocked_application)
-    manager.initialize()
-
-    assert "normal" in manager.getQualityGroupsForMachineDefinition(mocked_stack)
-
-
 def test_getQualityChangesGroup(quality_mocked_application):
     manager = QualityManager(quality_mocked_application)
     manager.initialize()