diff --git a/cura/Settings/SettingInheritanceManager.py b/cura/Settings/SettingInheritanceManager.py
index 6560f2b227..735feeee99 100644
--- a/cura/Settings/SettingInheritanceManager.py
+++ b/cura/Settings/SettingInheritanceManager.py
@@ -32,6 +32,7 @@ class SettingInheritanceManager(QObject):
     def getChildrenKeysWithOverride(self, key):
         definitions = self._global_container_stack.getBottom().findDefinitions(key=key)
         if not definitions:
+            Logger.log("w", "Could not find definition for key [%s]", key)
             return []
         result = []
         for key in definitions[0].getAllKeys():
@@ -51,6 +52,7 @@ class SettingInheritanceManager(QObject):
 
         definitions = self._global_container_stack.getBottom().findDefinitions(key=key)
         if not definitions:
+            Logger.log("w", "Could not find definition for key [%s] (2)", key)
             return []
         result = []
         for key in definitions[0].getAllKeys():
diff --git a/plugins/3MFReader/WorkspaceDialog.py b/plugins/3MFReader/WorkspaceDialog.py
index dadfe60d73..e3425078e7 100644
--- a/plugins/3MFReader/WorkspaceDialog.py
+++ b/plugins/3MFReader/WorkspaceDialog.py
@@ -144,6 +144,11 @@ class WorkspaceDialog(QObject):
         if key in self._result:
             self._result[key] = strategy
 
+    ##  Close the backend: otherwise one could end up with "Slicing..."
+    @pyqtSlot()
+    def closeBackend(self):
+        Application.getInstance().getBackend().close()
+
     def setMaterialConflict(self, material_conflict):
         self._has_material_conflict = material_conflict
         self.materialConflictChanged.emit()
diff --git a/plugins/3MFReader/WorkspaceDialog.qml b/plugins/3MFReader/WorkspaceDialog.qml
index 16e012dcef..fa69bc08c7 100644
--- a/plugins/3MFReader/WorkspaceDialog.qml
+++ b/plugins/3MFReader/WorkspaceDialog.qml
@@ -305,7 +305,7 @@ UM.Dialog
         {
             id: ok_button
             text: catalog.i18nc("@action:button","OK");
-            onClicked: { manager.onOkButtonClicked() }
+            onClicked: { manager.closeBackend(); manager.onOkButtonClicked() }
             enabled: true
         },
         Button
diff --git a/plugins/CuraEngineBackend/CuraEngineBackend.py b/plugins/CuraEngineBackend/CuraEngineBackend.py
index 9d448e11bb..b2df2563d0 100644
--- a/plugins/CuraEngineBackend/CuraEngineBackend.py
+++ b/plugins/CuraEngineBackend/CuraEngineBackend.py
@@ -149,6 +149,7 @@ class CuraEngineBackend(Backend):
 
     ##  Perform a slice of the scene.
     def slice(self):
+        Logger.log("d", "Starting slice job...")
         self._slice_start_time = time()
         if not self._enabled or not self._global_container_stack:  # We shouldn't be slicing.
             # try again in a short time
diff --git a/resources/qml/Settings/SettingItem.qml b/resources/qml/Settings/SettingItem.qml
index 7a1f99961b..7b50809baa 100644
--- a/resources/qml/Settings/SettingItem.qml
+++ b/resources/qml/Settings/SettingItem.qml
@@ -230,6 +230,10 @@ Item {
                     }
 
                     // Setting does have a limit_to_extruder property, so use that one instead.
+                    if (definition.key === undefined) {
+                        // Observed when loading workspace, probably when SettingItems are removed.
+                        return false;
+                    }
                     return Cura.SettingInheritanceManager.getOverridesForExtruder(definition.key, globalPropertyProvider.properties.limit_to_extruder).indexOf(definition.key) >= 0;
                 }