Another function that needs to wait for the uithread to get called.

PrintLevelWizard.cs

@@ -373,6 +373,11 @@ namespace MatterHackers.MatterControl
         }
 
         void DoneButton_Click(object sender, MouseEventArgs mouseEvent)
+        {
+            UiThread.RunOnIdle(DoDoneButton_Click);
+        }
+
+        void DoDoneButton_Click(object state)
         {
             Close();
         }