Mobile menu is underlaid beneath the page heading.

When the page is reduced to the width that uses the mobile menu, the submenus drop below the page heading. Those menu items are then inaccessible.

Not happening on every page, maybe has something to do with the layering/z-index of the cover block or Group block?

I tried adding z-index to the menu but it didn’t seem to help.

Here’s what I’ve tried (in the CSS Customizer)

.wp-block-navigation__submenu-container {
overflow: visible !important;
z-index: 9999999999;
}

The page I need help with: [log in to see the link]