I've got a blog with numerous older posts. In these posts are images (partly "pure" images, i.e. each image inserted seperately, partly as galleries) but no post thumbnails specified (as the feature "post thumbnail" was not present at the time of writing these posts).
I now used the plugin "Generate Post Thumbnails" to generate thumbnails for those posts and the plugin "Regenerate Thumbnails" to create the right-sized thumbnails needed.
Now I have the problem, that in the backend on some posts I see the generated thumbnail in the column "post thumbnails" but when I edit this post, there is no post thumbnail selected. In the frontend to these posts the post thumbnails are not shown.
I figured out that it has to do something with "pure" images vs. galleries in the text as the problem occures on all the posts in which I have a gallery (and not on these with "pure" images). In other words: in the posts list all posts now show a (correct) post thumbnail but in the frontend and the post edit those posts in which the images are inserted as a gallery do not.
Do you have an idea, how to fix this problem?
Thanks in advance!