The sidebar rendering at the bottom of a blog is generally a symptom of having an unclosed <div> tag in your blog template markup. The most common cause results from if you have an opening or closing <div> within an if statement in your Blog Content module markup.
To resolve:
Navigate in HubSpot to your blog template and ensure that all of your <div> are evenly wrapped inside or outside of if statements.
Incorrect example, where the sidebar would show below the blog, if the blog author is not defined:
<div> {% if content.blog_post_author %} </div> {% endif %}
Correct example, where the div would only render if the author was defined:
{% if content.blog_post_author %} <div> </div> {% endif %}
If you are still seeing an issue, make sure that there are the same number of opening and closing <div> tags in the markup.