I noticed this weird ad placement below on one of our blogs.
After troubleshooting for some minutes, I discovered that it was placed there by the “Insert Post Ads” plugin. The ad suppose to display “after content” i.e below blog post but displaying below the blog. Problem temporarily fixed by unpublishing the ad unit though.
Still trying to figure out the plugin that is making the ad not to display below the blog post.
The weird placement actually triggered a warning from Google Adsense though 
So, if you’re using the plugin and notice weird ad placement on your blog, now you know what’s up.