Sub-menu overlay problem

Hi folks
I've recently changed a client's menu to JUX Mega as it's easy to use for both vertical and horizontal menus. I don't use responsive hamburger style menu as the menu has only three top menu items. One of them has sub-menu items.

The issue is that the sub-menu window does not cover the sidebar menu module in small screens. It has something to do with the actual sidebar menu module, also a JUX. When placing some other module on the sidebar menu position, the opened sub-menu covers it, as it should do which of course also is the case position right under on big screens.

Image 1 - opened sub-menu on a big screen
Image 2 - opened sidebar on a small screen with the sub-menu ending up under the sidebar menu module.
Image 3 - opened sidebar on a small screen with a different module replacing the sidebar menu module, showing the sub-menu on top of an alternative module in the position of the sidebar menu.

A hint on how to get around this?

All the best
Erik L.

The link function did not work, so below are the links to the images.
Image 1: tinyurl.com/24oofrn7
Image 2: tinyurl.com/294vphnf
Image 3: tinyurl.com/2yq653mt

Hi Jackie and thank you very much!

The css code works like a charm.

Thank again and all the best.
Erik