Text Spacing Problem (+ single stack lists)

I recently started using a Single Stack List on a “View Post” page to filter the post’s author, and since then, the page’s body text no longer starts where it used to, under where the single stack list ends. Instead, it begins near the middle of the page, as if something is pushing the text down (see screenshot). What is going on here? How can I get the text to start from the top of the screen again?