The Divi menu module dropdown has the same width as it’s parent container. If the container is as small as the hamburger icon on tablets and mobile, the drop down is just as small and the content doesn’t fit. If this issue occurs depends on the design, it does when you follow this tutorial.

To fix it, use the following css in the Row Settings > Advanced > Custom CSS > Free Form CSS:

@media (max-width: 980px) {
#et-boc.et-boc selector .et_pb_column,
#et-boc.et-boc selector .et_pb_menu, #et-boc.et-boc selector .et_pb_menu_inner_container{
    position: static !important;
}
}Code language: CSS (css)