Users always ask about sidebar dropping below the content. The main reason is the presence of HTML or CSS error in your theme. This kind of error can be fixed in many ways that are quick and simple. This problem is common when you install a plugin and get to see this error immediately after it. The easy solution that one can do is disabling that plugin and then refreshing to see if the error is rectified. If a user has not closed the Div tags then also you can get this problem. So, make sure to fix the unclosed or an extra closing <div> tag. This is the most common cause that can make you happen the occurrence of sidebar below content error.
The width ratio settings on your page are also a reason behind this problem. So, youll have to fix this to ensure the proper functioning of WordPress. You can also get in touch with the WordPress experts.