Now I'm seeing this behavior on an inherited development site hosted on I believe, a MODX Cloud Lab account (moving it to a real server this week - via copy and paste due to other non-MODX issues).
I've played with furl's, caching (caching was disabled, now is back on), and checked into everything I can think of but I can't see why it's loading the container twice. .htaccess is not part of the issue, being that the site is on MODX Cloud. Interestingly enough, after a full cache clear, or if loading the container for the first time from the landing page the menu links appear correct. Then, one link can be clicked (doesn't matter which), and the child page loads properly. After that, all the menu links contain duplicate parents in the url (
http://sitename.com/parent/parent/resource.html) and navigation is impossible.
What's even stranger, is that another parent and it's child resources do not do this.
My next step is to duplicate these pages from scratch and see if I can get it to replicate.