Ah, are we talking about the secondary navigation?
As of right now, we rely on some simple javascript to move the secondary navigation after the primary navigation when it exists in the sidebar. It’s not a perfect solution, but it prevents having to render the secondary navigation multiple times on the page and hiding one for the mobile.
It’s an issue on AMP sites as they don’t allow for javascript. Unfortunately there is no solution as of right now without actually moving your secondary navigation out of the sidebar.
I’ve made a note of this, as it’s time to move away from that javascript solution.