Below is the Stack Trace that you asked. It is always on SyncFusion components and as I mentioned it happened all of a sudden. However, your question triggered me thinking which other "innocuous" changes may have triggered these faults. Well, as it turns out I had added the following line to my Program.cs before instantiating the main form:
SkinManager.ApplicationVisualTheme = Properties.Settings.Default.Theme;
And that Theme is defined in my application settings and it is set to "PurpleRain" which is the exact same name of the theme DLL I created with Theme Studio and referenced in my application. The theme is properly applied to the few components that are themeable (unfortunately it does not work for regular WinForms components). So, I figured the only change was the addition to the call to SkinManager.ApplicationVisualTheme property and voilá! when I remove the call to the SkinManager, the NullReferenceException goes away and the PurpleRain theme is (still) applied to the NavigationDrawer and a few other SF components where I programmatically set the ThemeName property. The documentation led me to believe I could save myself from manually setting the ThemeName on each and every control by simply using the Skin Manager but that approach seems to be flawed because using the Skin Manager to set the Application Visual Theme breaks everything! if I leave SkinManager.LoadAssembly(typeof(PurpleRain).Assembly) no errors are produced and the theme is available BUT as I said, adding a call to ApplicationVisualTheme causes random Null Reference Exceptions on SF components during InitializeComponent.
Message=Referencia a objeto no establecida como instancia de un objeto.
at Syncfusion.Windows.Forms.Tools.AutoLabel.ApplyControlTheme(String themeName)
at Syncfusion.Windows.Forms.Tools.AutoLabel.set_ThemeName(String value)
at Syncfusion.Windows.Forms.Tools.AutoLabel.Syncfusion.Windows.Forms.IVisualStyle.set_VisualTheme(String value)
at Syncfusion.Windows.Forms.SkinManager.ApplyThemeToControls(Control control, String visualStyle)
at Syncfusion.Windows.Forms.SkinManager.SetVisualStyle(Control control, String visualStyle)
at MyNovel.UI.Views.Viewlets.SimpleRichEditorViewlet.InitializeComponent() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Views\Viewlets\SimpleRichEditorViewlet.Designer.cs:line 43
at MyNovel.UI.Views.Viewlets.SimpleRichEditorViewlet..ctor() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Views\Viewlets\SimpleRichEditorViewlet.cs:line 50
at MyNovel.UI.Views.Viewlets.FreeRichTextViewlet.InitializeComponent() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Views\Viewlets\FreeRichTextViewlet.Designer.cs:line 38
at MyNovel.UI.Views.Viewlets.FreeRichTextViewlet..ctor() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Views\Viewlets\FreeRichTextViewlet.cs:line 26
at MyNovel.UI.Views.NovelixView.InitializeComponent() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Views\NovelixView.Designer.cs:line 41
at MyNovel.UI.Views.NovelixView..ctor() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Views\NovelixView.cs:line 27
at MyNovel.UI.Program.Main() in C:\Users\Didi\source\repos\MyNovel\MyNovel.UI\Program.cs:line 27