Blog subscription sends duplicate emails

We have a blog that is sending duplicate post emails to some, but not all, of the blog subscribers. In today's instance, the blog's author did not receive the post, but his manger received it, and his manager's manager received two emails for the same post. I'm also a subscriber and received two emails for the same post. The email logs confirmed all this. The profile settings all look good and the only complaint is coming in for this one blog. 

One other note. We had an issue with this blog several months back where the owner/author stopped getting the posts. As we were troubleshooting the issue resolved itself. Now he's back to not getting the posts. I cannot see anything obviously wrong with the way this blog is set up. Any ideas on where else we can troubleshoot? Thanks.