BuddyPress.org

The wrong thing was that you assigned a parent to a BP page. 😉
(your-site/community/my-stuff/activate) activate was parent of my-stuff !

BP comp’ pages are not working as ordinary WP pages. They should stay blank, without any template or parent page. Just a title and basta. They are in for internal usage only, WP’s page system gives the url and that’s enough for BP which will add fully dynamically content, depending the member and the current action.
WP pages are static. BP’s are … ? Yes !