after viewing a related earlier support thread I addressed my problem by adjusting the trigger point of the mobile menu display in Theme Option > Advanced Settings
@media (max-width: 979px) {
#nav-main ul.sf-menu {display: block;}
#mobile-nav-trigger {display: none;}
#nav-second ul.sf-menu {display: block;}
}
@media (max-width: 15px) {
#nav-main ul.sf-menu {display: none;}
#mobile-nav-trigger {display: block;}
#nav-second ul.sf-menu {display: none;}
}