The code you posted, and which I amended, is unsuitable for content controls. It is for legacy form fields, which your original code actually references.
You can't mix content controls and form fields in the same document, and content controls should not be protected as forms.
For content controls you need the following in the ThisDocument module of the document and the document should be protected as read only, with editors to mark the controls as editable. See https://www.gmayor.com/insert_content_control_addin.htm 
Private Sub Document_ContentControlOnExit(ByVal ContentControl As ContentControl, Cancel As Boolean)
Dim oRng As Range
    If ContentControl.ShowingPlaceholderText = False Then
        Select Case ContentControl.Title
            Case "DD33"
                With ContentControl
                    If UCase(.Range.Text) = "NON" Then
                        If Not ActiveDocument.ProtectionType = wdNoProtection Then
                            ActiveDocument.Unprotect Password:=""
                        End If
                        .LockContentControl = False
                        Set oRng = .Range
                        .Delete
                        oRng.Text = ""
                        ActiveDocument.Protect Type:=wdAllowOnlyReading, Password:=""
                    End If
                End With
            Case Else
        End Select
    End If
End Sub