diff --git a/src/MahApps.Metro/Behaviors/WindowsSettingBehavior.cs b/src/MahApps.Metro/Behaviors/WindowsSettingBehavior.cs
index d144e11e6d..c9bf1edb1a 100644
--- a/src/MahApps.Metro/Behaviors/WindowsSettingBehavior.cs
+++ b/src/MahApps.Metro/Behaviors/WindowsSettingBehavior.cs
@@ -46,15 +46,14 @@ private void AssociatedObject_SourceInitialized(object sender, EventArgs e)
             window.Closing += this.AssociatedObject_Closing;
             window.Closed += this.AssociatedObject_Closed;
 
-            // This operation must be thread safe
-            window.BeginInvoke(() =>
+            // This operation must be thread safe. It is possible, that the window is running in a different Thread.
+            Application.Current?.BeginInvoke(app =>
                 {
-                    var application = Application.Current;
-                    if (application != null)
+                    if (app != null)
                     {
-                        application.SessionEnding += this.CurrentApplicationSessionEnding;
+                        app.SessionEnding += this.CurrentApplicationSessionEnding;
                     }
-                }); 
+                });
         }
 
         private void AssociatedObject_Closing(object sender, System.ComponentModel.CancelEventArgs e)
@@ -100,12 +99,11 @@ private void CleanUp(string fromWhere)
             window.SourceInitialized -= this.AssociatedObject_SourceInitialized;
 
             // This operation must be thread safe
-            window.BeginInvoke(() =>
+            Application.Current?.BeginInvoke(app =>
                 {
-                    var application = Application.Current;
-                    if (application != null)
+                    if (app != null)
                     {
-                        application.SessionEnding -= this.CurrentApplicationSessionEnding;
+                        app.SessionEnding -= this.CurrentApplicationSessionEnding;
                     }
                 });
         }
diff --git a/src/MahApps.Metro/Controls/Extensions.cs b/src/MahApps.Metro/Controls/Extensions.cs
index c90df105ba..534bc1ee65 100644
--- a/src/MahApps.Metro/Controls/Extensions.cs
+++ b/src/MahApps.Metro/Controls/Extensions.cs
@@ -73,7 +73,7 @@ public static void BeginInvoke([NotNull] this DispatcherObject dispatcherObject,
                 throw new ArgumentNullException(nameof(invokeAction));
             }
 
-            dispatcherObject.Dispatcher.BeginInvoke(priority, invokeAction);
+            dispatcherObject.Dispatcher?.BeginInvoke(priority, invokeAction);
         }
 
         public static void BeginInvoke<T>([NotNull] this T dispatcherObject, [NotNull] Action<T> invokeAction, DispatcherPriority priority = DispatcherPriority.Background)
diff --git a/src/MahApps.Metro/Themes/DateTimePicker.xaml b/src/MahApps.Metro/Themes/DateTimePicker.xaml
index 8c86d0542d..1e630079fe 100644
--- a/src/MahApps.Metro/Themes/DateTimePicker.xaml
+++ b/src/MahApps.Metro/Themes/DateTimePicker.xaml
@@ -441,7 +441,6 @@
 
                         <Trigger Property="IsClockVisible" Value="False">
                             <Setter TargetName="PART_Clock" Property="Visibility" Value="Collapsed" />
-                            <Setter TargetName="PART_ClockPartSelectorsHolder" Property="Visibility" Value="Collapsed" />
                         </Trigger>
                         <Trigger Property="IsDatePickerVisible" Value="True">
                             <Setter TargetName="PART_Calendar" Property="Visibility" Value="Visible" />
@@ -474,10 +473,10 @@
                                 <Condition Binding="{Binding Path=(mah:TextBoxHelper.HasText), RelativeSource={RelativeSource Self}}" Value="True" />
                             </MultiDataTrigger.Conditions>
                             <MultiDataTrigger.EnterActions>
-                                <BeginStoryboard Storyboard="{DynamicResource MahApps.Storyboard.ShowFloatingMessage}" />
+                                <BeginStoryboard Storyboard="{StaticResource MahApps.Storyboard.ShowFloatingMessage}" />
                             </MultiDataTrigger.EnterActions>
                             <MultiDataTrigger.ExitActions>
-                                <BeginStoryboard Storyboard="{DynamicResource MahApps.Storyboard.HideFloatingMessage}" />
+                                <BeginStoryboard Storyboard="{StaticResource MahApps.Storyboard.HideFloatingMessage}" />
                             </MultiDataTrigger.ExitActions>
                         </MultiDataTrigger>