Menu overlay ends up under elements

Im using the full page menu in a sticky navheader and when I scroll down past the first section on the page and then open the menu the elements in the visible section end up on top of the menu and background overlay instead of being covered by it.
I’ve tried changing the z index of the various elements and the menu itself but nothing helps.

Is there a solution for this? I need the open menu to always appear on top no matter where in the page I’ve scrolled own to.