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 
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Thank you for reporting this bug. I could not reproduce it.
Firstly, when I updated the category to icon, I didn’t need to rebake.
My second test was to force rebake, and the lightbox for CNN and YouTube was generated correctly. I recorded my screen.
Were your steps the same?
2 Likes
I didn’t give it a seconds try. When I saw things were made “worse” I thought, let’s just restore the latest backup and get proper advice on how to correct all category tag icons in posts 
I could try again soon, if this is really a proper way to fix it. At the time I knew I was doing something risky, but I thought it would be worth it. My forum isn’t that popular, I could do some experiments (after backing up of course). One downside I also noticed was that some websites are not available anymore. So the HTML previews would never restore. So ideally I only update categories. But I suppose such a HTML rebake is not possible.