How to programatically move Appointment items to a new PST using C# Outlook Interop

Question

I would like to move Appointment items, both from msg files and from a PST, to a new separate PST. However I continually get errors.

Here is my latest attempt for moving msg files, my code is similar with PSTs, except the Item is created from a folder loop of the PST. ReleaseObj class is just a class that checks if an object is null, and if not calls Marshal.ReleaseComObject:

        Stores stores = null;
        Store currStore = null;
        Folder newPSTRootFolder = null;
        Folder msgAddFolder = null;
        Folder appointmentAddFolder = null;

        try
        {
            outlookNs = app.Session;
            outlookNs.AddStore(newPSTFile);
            
            //Create Calendar folder for appointments
            appointmentAddFolder = outlookNs.GetDefaultFolder(OlDefaultFolders.olFolderCalendar) as Folder;
            
            stores = outlookNs.Stores;
            for (int i = 1; i <= stores.Count; i++)
            {
                currStore = stores[i];
                if (currStore.FilePath == newPSTFile)
                {
                    newPSTRootFolder = (Folder)currStore.GetRootFolder();
                    msgAddFolder = newPSTRootFolder.Folders.Add(customFolder, Type.Missing) as Folder;
                }
                ReleaseObj(currStore);
            }

            string[] msgFilesPull = Directory.GetFiles(msgFolder, "*.msg", SearchOption.AllDirectories);

            foreach(string msgFile in msgFilesPull)
            {
                try
                {
                    var item = app.Session.OpenSharedItem(msgFile);

                    if (item is MailItem mailItem)
                    {
                        mailItem.Move(msgAddFolder as Folder);

                        ReleaseObj(item);
                        ReleaseObj(mailItem);
                    }
                    else if (item is ContactItem contactItem)
                    {
                        contactItem.Move(msgAddFolder as Folder);

                        ReleaseObj(item);
                        ReleaseObj(contactItem);
                    }
                    else if (item is AppointmentItem appointmentItem)
                    {
                        appointmentItem.Move(appointmentAddFolder as Folder);

                        ReleaseObj(item);
                        ReleaseObj(appointmentItem);
                    }
                    else if (item is TaskItem taskItem)
                    {
                        taskItem.Move(msgAddFolder as Folder);

                        ReleaseObj(item);
                        ReleaseObj(taskItem);
                    }
                    else if (item is MeetingItem meetingItem)
                    {
                        meetingItem.Move(msgAddFolder as Folder);

                        ReleaseObj(item);
                        ReleaseObj(meetingItem);
                    }

                    ReleaseObj(item);
                }
                catch (System.Exception ex)
                {
                    MessageBox.Show($"ERROR\nCould not add {msgFile}\n{ex}");
                }                    
            }
        }

The above code fails to adds the Appointment, with a generic "COMException(0x80040201): The Operation Failed.

I have also tried just adding the Appointment to the newly created msgAddFolder, but get an error that the folder is the wrong type.

Is there any way I can actually accomplish this?