Cover and Modal elements have been given a much higher z-index to make sure they fall on top of all other elements.

sass/mixins.scss

 
 @mixin cover(){
   position: fixed; /* Stay in place */
-  z-index: 1; /* Sit on top */
+  z-index: 100; /* Sit on top */
   left: 0;
   top: 0;
   width: 100%; /* Full width */