VB.Net - Program Soft Locks When Removing a User from All AD Groups

Question

I'm writing an application in VB.Net which accepts an AD account input by the user and deprovisions and disables it automatically. As part of this, it strips all AD groups it can from the user.

Note that certain users may be members of groups that the person running the program does not have permission to modify, and that's OK for my requirements. These groups do not have a standard naming convention or format.

The following code removes the user from all groups they are a member of successfully, skipping any groups the person operating the program does not have permission to modify, but the catch is the program then appears to soft lock after attempting to remove a group it cannot (such as Domain Users)! What can I do to prevent this?

Dim ctx As DirectoryServices.AccountManagement.PrincipalContext = New DirectoryServices.AccountManagement.PrincipalContext(DirectoryServices.AccountManagement.ContextType.Domain, "net.mydomain.co.uk")
Dim user As DirectoryServices.AccountManagement.UserPrincipal = DirectoryServices.AccountManagement.UserPrincipal.FindByIdentity(ctx, tbxUsertoDeprovision.Text)
For Each group As DirectoryServices.AccountManagement.GroupPrincipal In user.GetGroups(ctx)
    Try
        group.Members.Remove(user)
        group.Save()
        group.Dispose()
    Catch ex As Exception
        Continue For
    End Try
Next

If I insert a Message Box into the Catch as follows:

Catch ex As Exception
    MessageBox.Show(ex.ToString())
    Continue For

Then run the code, it displays the following message box, but only once:

System.InvalidOperation.Exception: The member can not be removed from the Group object's Members property because it has this group as its primary group. (This is at the group.Members.Remove(user) line).

The program then goes no further and no code after Next is ever executed. I'm forced to close the application.