It's taken me longer than I'd like to figure out how to update an Article using the Script API (partly due it not updating the article without the ReadyToPublish parameter being set to True).
The script should look something like this;
$articles_v1_articleVersions.Create($article.Title, $body, $article.Type.Id, "%{ ArticleId = $article.ContentId, ReadyToPublish = 'True', SuppressNotifications = 'True' }")
Now that's working, I've noticed that as soon as I edit the Article normally using the website, the Categories I initially had set are blank..
Why does it blank the categories when I create a new Article version instead of carrying across what it had before? Tags are carried across without the need to set them again 
Do I need to list the categories on the current version first, then re-apply them after the new version has saved? That seems a bit of a faff, so I feel like I'm missing something obvious.
