I’ve switched now to the native category icons, but I need to regenerate the HTML for the topics that still use the old style. Otherwise the icon is just a gray square.
Is a rake posts:rebake fine to run? I have about 8000 posts that would be rebaked, so that’s doable. What do you recommend?
Edit:
I did a rebake, that works! 
However, on many posts the URLs aren’t showing the previews. Meaning for example that an article on cnn.com doesn’t show the title of the article. But just the verbatim URL. Also some YouTube thumbnails are not generated. Is there a way to fix this as well?
Second edit: I’ve restored a backup and will wait for an answer to correctly address just the category icons 