Yes, my plugin will not create featured images for posts that already have them attached. Yes, I have been thinking about adding an option to the bulk utility that will unset all featured images and recreate them. I will add this to the next version.
Pertaining to how it sometimes creates images with the text “auto draft,” this is a bug. I will attempt to fix it in the next version as well.
Regarding the text not updating when you update the post title, I may be able to add an option for this in the next version as well. But, yes, the only way to do this now is to unset the featured image (or delete it) and then resave the post.