diff --git a/cura/MachineAction.py b/cura/MachineAction.py
index b9ff938303..c4553bc1e4 100644
--- a/cura/MachineAction.py
+++ b/cura/MachineAction.py
@@ -6,13 +6,21 @@ from PyQt5.QtQml import QQmlComponent, QQmlContext
 
 from UM.PluginObject import PluginObject
 from UM.PluginRegistry import PluginRegistry
-
+from UM.Logger import Logger
 from UM.Application import Application
 
 import os
 
 
+##  Machine actions are actions that are added to a specific machine type. Examples of such actions are
+#   updating the firmware, connecting with remote devices or doing bed leveling. A machine action can also have a
+#   qml, which should contain a "Cura.MachineAction" item. When activated, the item will be displayed in a dialog
+#   and this object will be added as "manager" (so all pyqtSlot() functions can be called by calling manager.func())
 class MachineAction(QObject, PluginObject):
+
+    ##  Create a new Machine action.
+    #   \param key unique key of the machine action
+    #   \param label Human readable label used to identify the machine action.
     def __init__(self, key, label = ""):
         super().__init__()
         self._key = key
@@ -63,13 +71,16 @@ class MachineAction(QObject, PluginObject):
     def finished(self):
         return self._finished
 
+    ##  Protected helper to create a view object based on provided QML.
     def _createViewFromQML(self):
-        path = QUrl.fromLocalFile(
-            os.path.join(PluginRegistry.getInstance().getPluginPath(self.getPluginId()), self._qml_url))
+        path = QUrl.fromLocalFile(os.path.join(PluginRegistry.getInstance().getPluginPath(self.getPluginId()), self._qml_url))
         self._component = QQmlComponent(Application.getInstance()._engine, path)
         self._context = QQmlContext(Application.getInstance()._engine.rootContext())
         self._context.setContextProperty("manager", self)
         self._view = self._component.create(self._context)
+        if self._view is None:
+            Logger.log("c", "QQmlComponent status %s", self._component.status())
+            Logger.log("c", "QQmlComponent error string %s", self._component.errorString())
 
     @pyqtProperty(QObject, constant = True)
     def displayItem(self):
diff --git a/plugins/UltimakerMachineActions/BedLevelMachineAction.py b/plugins/UltimakerMachineActions/BedLevelMachineAction.py
index c80a8ffc01..117b2c99e2 100644
--- a/plugins/UltimakerMachineActions/BedLevelMachineAction.py
+++ b/plugins/UltimakerMachineActions/BedLevelMachineAction.py
@@ -8,6 +8,8 @@ from UM.i18n import i18nCatalog
 catalog = i18nCatalog("cura")
 
 
+##  A simple action to handle manual bed leveling procedure for printers that don't have it on the firmware.
+#   This is currently only used by the Ultimaker Original+
 class BedLevelMachineAction(MachineAction):
     def __init__(self):
         super().__init__("BedLevel", catalog.i18nc("@action", "Level build plate"))
diff --git a/plugins/UltimakerMachineActions/UMOCheckupMachineAction.py b/plugins/UltimakerMachineActions/UMOCheckupMachineAction.py
index 355b4dd0c1..f9ad4789e5 100644
--- a/plugins/UltimakerMachineActions/UMOCheckupMachineAction.py
+++ b/plugins/UltimakerMachineActions/UMOCheckupMachineAction.py
@@ -8,6 +8,7 @@ from UM.i18n import i18nCatalog
 catalog = i18nCatalog("cura")
 
 
+##  Action to check up if the self-built UMO was done correctly.
 class UMOCheckupMachineAction(MachineAction):
     def __init__(self):
         super().__init__("UMOCheckup", catalog.i18nc("@action", "Checkup"))
@@ -27,7 +28,6 @@ class UMOCheckupMachineAction(MachineAction):
 
         Application.getInstance().getOutputDeviceManager().outputDevicesChanged.connect(self._onOutputDevicesChanged)
 
-
     onBedTestCompleted = pyqtSignal()
     onHotendTestCompleted = pyqtSignal()
 
diff --git a/plugins/UltimakerMachineActions/UMOUpgradeSelection.py b/plugins/UltimakerMachineActions/UMOUpgradeSelection.py
index e85ec7b434..a9148e0c7b 100644
--- a/plugins/UltimakerMachineActions/UMOUpgradeSelection.py
+++ b/plugins/UltimakerMachineActions/UMOUpgradeSelection.py
@@ -7,6 +7,9 @@ catalog = i18nCatalog("cura")
 
 import UM.Settings.InstanceContainer
 
+
+##  The Ultimaker Original can have a few revisions & upgrades. This action helps with selecting them, so they are added
+#   as a variant.
 class UMOUpgradeSelection(MachineAction):
     def __init__(self):
         super().__init__("UMOUpgradeSelection", catalog.i18nc("@action", "Select upgrades"))
diff --git a/plugins/UltimakerMachineActions/UpgradeFirmwareMachineAction.py b/plugins/UltimakerMachineActions/UpgradeFirmwareMachineAction.py
index 71d3f0b55b..828411cc8a 100644
--- a/plugins/UltimakerMachineActions/UpgradeFirmwareMachineAction.py
+++ b/plugins/UltimakerMachineActions/UpgradeFirmwareMachineAction.py
@@ -5,6 +5,7 @@ import UM.Settings.DefinitionContainer
 catalog = i18nCatalog("cura")
 
 
+##  Upgrade the firmware of a machine by USB with this action.
 class UpgradeFirmwareMachineAction(MachineAction):
     def __init__(self):
         super().__init__("UpgradeFirmware", catalog.i18nc("@action", "Upgrade Firmware"))
@@ -12,6 +13,6 @@ class UpgradeFirmwareMachineAction(MachineAction):
         cura.Settings.CuraContainerRegistry.getInstance().containerAdded.connect(self._onContainerAdded)
 
     def _onContainerAdded(self, container):
-        # Add this action as a supported action to all machine definitions
+        # Add this action as a supported action to all machine definitions if they support USB connection
         if isinstance(container, UM.Settings.DefinitionContainer) and container.getMetaDataEntry("type") == "machine" and container.getMetaDataEntry("supports_usb_connection"):
             UM.Application.getInstance().getMachineActionManager().addSupportedAction(container.getId(), self.getKey())