I've noticed that when porting non-boost based themes to Moodle 3.2 and 3.3 where you previously have the ajax/expandable navigation that let you drill down to deep settings now just navigates to whatever you clicked on. Now to get to a deep setting (like site administration > appearance > themes > theme settings) now means you get a page refresh when you click on site adminstration, then another refresh when you click on appearance, then another refresh when you click on themes, then another refresh when you click on settings. In the past you were able to expand the navigation all the way down and it wouldn't refresh until you clicked on the item you wanted. Is that an intended change or something in the theme that I can change?
Moodle 3.3 site admin navigation (NOT boost theme)
I think if you go to Site Admin->Appearance->Navigation there is an option for Link Admin Categories that displays the expandable sections as links. It's set to yes by default. Try unchecking that box and see if that fixes the issue.