NIGHTMARE drupal primary links menu active highlight issue: duplicate menu path entries.
Avoid duplicating paths in your Drupal Menu system — the menu administration does NOT prevent you from having menus with similar paths, and actually, will chug along quite happily with duplicated path names — that is, until you try to troubleshoot while menu highlighting isn’t working for one particular node type.
Even worse, it’ll highlight unevenly — MENU_DEFAULT_LOCAL_TASK ? the proper primary link is highlighted. MENU_LOCAL_TASK? No highlight.
The drupal menu system should actively prevent the user from duping paths, or launch an error if it discovers a newly installed module dupes a user created path.
But for now, if you’re having difficult to fix menu problems, buzz through your menu table and make sure you have unique paths for everything.
(How did I get dupe paths? Well, during the lag between a menu cache refresh — which Drupal needs to add an admin button to force — I stupidly added a menu with the same path as my MENU_NORMAL_ITEM — then deleted it. Alas, it was not actually deleted — just hidden.).
