BuddyPress.org

Hi everyone,
I have the following problem:
When I change the Group Tab names and reorder them, it is not possible to create a new Group.
it returns an 500 error when I come to the second creation step which comes from my Group Extension where I created a new Group Tab.
Its maybe important to know that I changed the default Group Tab with:

define( 'BP_GROUPS_DEFAULT_EXTENSION', 'my_new_tab_slug' );

I used the action hook and function described in the Navigation API of the documentation.

my Snippet is:

//Action to rename Group Tabs
add_action( 'bp_actions', 'bp_change_group_tabs');
//Function to Rename Group Tabs
function bp_change_group_tabs() {

    if ( ! bp_is_group() ) {
        return;
    }
     buddypress()->groups->nav->edit_nav( array( 'name' => __( 'Projekteinstellungen', 'buddypress' ) ), 'admin', bp_current_item() );
     buddypress()->groups->nav->edit_nav( array( 'name' => __( 'Dozenten einladen', 'buddypress' ) ), 'invite-anyone', bp_current_item() );
     buddypress()->groups->nav->edit_nav( array( 'name' => __( 'Dokumente', 'buddypress' ) ), 'docs', bp_current_item() );
     buddypress()->groups->nav->edit_nav( array( 'name' => __( 'Projektaktivität', 'buddypress' ) ), 'home', bp_current_item() );

     buddypress()->groups->nav->edit_nav( array( 'position' => 2 ), 'home', bp_current_item() );
     buddypress()->groups->nav->edit_nav( array( 'position' => 5 ), 'docs', bp_current_item() );
}

When I decomment the buddypress()->groups->nav->edit_nav functions everything works again. Is this a bug?

Any help would be nice.
Thanks