Make sure you have the right arrow for the job. Literally. If you have a dropdown within a dropdown in your Divi primary menu, you will see that the dropdown uses the down arrow, indicating that the new submenu would appear underneath it. However, the dropdown actually appears to the right of the parent.
Thankfully, there’s a quick fix you can add to your child theme or Custom CSS in the theme options panel. Insert the following code and confuse your visitors no longer.
#top-menu li .menu-item-has-children>a:first-child:after { content: "\35"; }