Menu Block 7.x-2.2
Context: Menu Block 7.x-3.x-dev
Hopefully this is relevant to this particular module and not just to Context itself. Let's say that I have the following menu tree where two distinct submenus point to the same page:
I wanted to have context activate the 2nd instance of the submenu 1 because that's the "main" one. Even though I chose that exact one in the Context Menu Reaction select list, it only saved the link_path in the database, and thus when context_menu_block.module line 131 looked for a match to make active, it found the first instance and stopped looking for any others.
I solved this issue by changing the identifier from link_path/href to the unique mlid of the menu.
Change to Context module was context_reaction_menu.inc line 21.