explanation in comment

Src/Dnn/ToSic.Sxc.Dnn.Main/DnnBusinessController.cs

@@ -4,17 +4,21 @@
 // Note about the name
 // Some day we should change this namespace to ToSic.Sxc.Dnn.something
 // But we can't just do it, because the name is registered in Dnn DBs, so update-scripts would be needed
-// TODO: STV - WHY IS THIS NOT PART OF THE DnnBusinessController? it seems that that is already the term in the DB?
-
+// WHY IS THIS NOT PART OF THE DnnBusinessController? it seems that that is already the term in the DB?
+// Reason if that can't call StartupDnn().Configure() from ToSic.Sxc.Dnn.DnnBusinessController because of circular dependency
+// and need to configure DI before UpgradeModule to fix issue: "Module upgrade did not complete."
+// "System.ArgumentNullException: Value cannot be null. Parameter name: provider
+// at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
+// at ToSic.Eav.Factory.GetServiceProvider()"
 // ReSharper disable once CheckNamespace
 namespace ToSic.SexyContent
 {
     public class DnnBusinessController: ToSic.Sxc.Dnn.DnnBusinessController, IUpgradeable, IVersionable
     {
         public new string UpgradeModule(string version)
         {
-            new StartupDnn().Configure();
+            new StartupDnn().Configure(); // can't call it from ToSic.Sxc.Dnn.DnnBusinessController because of circular dependency
             return base.UpgradeModule(version);
         }
     }
-}
+}