Hi 
Older posts need to be rebaked. You can do manually that by clicking the three dots icon below the post, then the wrench, then Rebuild HTML.
If you have a lot of posts that need to be rebaked, you may need the rake task to rebake all posts or use a custom rails script to rebake just some of them using the needed criteria.
Something like this I think:
Post.where('raw LIKE ?', 'a specific URL').find_each do |p|
p.rebake!
end