Well, I wasn’t using a plugin for the initial content, just thinking I could use Post Snippets for what they will add later, but I tried it with just shortcodes and it works well enough. They’ll just have to learn how to identify shortcode blocks.
Incidentally, it DOES still happen when your plugin is deactivated so, not your problem I guess. Sorry for bothering you and thanks for all that you do. Your plugin is great!