Plugin: Generate Post Thumbnails

I have been trying to upgrade a blog with thousands of posts from one template that did not support thumbnails to one that does. The Generate Post Thumbnails plugin worked well, generating the majority of thumbnails and placing them in the /public_html/wp-content/uploads in dated folders. These in turn were recognized in the Dashboard’s Media Library and by my new template. However, the same plug-in seems to PUBLISH the thumbnail version of the first photo in any post above the full size version of the first photo of the post. In essence, you have a duplicate picture in every post. I don’t understand code enough to stop the publishing if the generated thumbnails or if its even possible. There must be a way to generate thumbs and link them to posts without actually publishing them physically?

I realize a lot of these types of questions die here. I’ve tried searching for answers. I would truly appreciate anyone’s assistance on this.

The WordPress Plugin can be found here: <link>https://www.ads-software.com/extend/plugins/generate-post-thumbnails/ </link>