Hi @properlypurple,
I’m not using a special plug-in for shortcodes, because I’ve only been using the Classic Widgets plug-in, which gives me a meta box (title, image upload, URL) so far. My theme is Newspaper, but the developer of TagDiv told me that the reason for this problem is not the theme.
If that is important: I’m not using Gutenberg, so I installed the Disable GUtenberg and Classic Widget plugins. I wonder if it helps to install the Classic Editor additionally? Since my tech colleague is on vacation, I’m trying to solve the problem myself, so forgive my half-knowledge.