Page menu drop downs appearing and disappearing

I have a strange issue going on. On my page drop downs, the theme is mysteriously only displaying child pages when the visitor is already on that page. If they are looking at any other page, they are not visible.

In other words, if I have drop down menus for Page 1, Page 2, and Page 3 (all top level parent pages), the drop down menu for Page 1 only shows up if I’m viewing Page 1, and the others are not visible. If I navigate to Page 2, the drop down menu for Page 2 appears (after Page 2 loads) but then the drop downs for Page 1 and Page 3 disappear.

I am stumped!