So I have a page model for Articles and several existing articles.   I've created a new field for Blog Categories that I want to batch update based on another field in the page model.   I'm having trouble applying the update and publishing.

This is my new field.

        [Display(GroupName = SystemTabNames.Content, Name = "Selected Blog Categories", Order = 5)]
        [SelectMany(SelectionFactoryType = typeof(BlogCategorySelectionFactory))]
        public virtual IList<string> ArticleBlogCategories { get; set; }

Here's the code snippet that is applying the update.   Currently I'm just updating one article to test.

                if (!string.IsNullOrEmpty(blogCategoryNames))
                {

                    var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
                    var editPage = contentLoader.Get<ArticlePage>(childPage.ContentLink);
                    var writableClone = editPage.CreateWritableClone() as ArticlePage;

                    writableClone.ArticleBlogCategories = new List<string>();
                    string[] arrayCategories = blogCategoryNames.Split(',');
                    foreach (var sub in arrayCategories)
                    {
                        writableClone.ArticleBlogCategories.Add(sub);
                    }

                    contentRepository.Save(writableClone, SaveAction.Publish | SaveAction.ForceNewVersion, AccessLevel.FullAccess);

                }

The code seems to execute fine, but when I go back to the page in the CMS, all of the fields are cleared and I cannot publish anymore but somehow I see the text in the presentation.   I have to revert back to the previous published version.   I only want to update this ArticleBlogCategories field.   When I create the WriteableClone, all of the fields seem to be there but the issues happen after the save.   Is there a problem with the syntax of the last line for contentRepository.Save?