Hmmm… complex one and correcting it may ‘change’ the other menu behaviour.
Try this CSS for the navigation stying instead:
@media (min-width: 769px) {
.main-navigation ul li {
position: relative;
}
.main-navigation ul > li > a:after {
content: '';
position: absolute;
height: 0;
width: 100%;
bottom: 0;
left: 0;
pointer-events: none;
filter: hue-rotation(90deg);
-webkit-filter: hue-rotation(90deg);
-webkit-transition: height 0.35s ease;
transition: height 0.35s ease;
background-color: red;
}
.main-navigation ul > li a:hover:after, .main-navigation ul li.current-menu-item a:after {
height: 6px;
}
}