So when I am in dual folder view, navigating in one pane automatically causes the exact same view in the two panes, which is never useful. I may as well use single pane mode in that case. It does seem that occasionally (and randomly as far as I can tell) the two panes become unsynced. How do I force the unsynced state when in dual folder view mode?
It sounds like you have turned Navigation Lock on, or set the two sides to be linked folder tabs with Navigation Lock.
You would normally have to go out of your way to do that, but if you saved the Default Lister after doing it then you might end up with it turned on in all new windows which you open.
If so, turn it off and save the Default Lister again.