As you see on the image there is no Target button to target the mobs.

The bug happens if you select the NPC without clicking to it on the list either:

-by only using the icons without clicking or collapsing any echology related list element in the menu.

-or if you kill a mob that gives you knowdolage and press the H afterwards.

Probably currently this button is shown when you click on echology related list elements only, instead of causing the button to be displayed when an NPC's echology information is displayed.