Hi all,
I just finished the Kazan mission of the Rus campaign, as the outer walls are connected to the inner walls, and I wanted to make sure I get the achievement for erasing all enemy production buildings + enemies I walked on the walls of the inner Kazan city before I breached the wall itself. Thus, my dudes unfortunately also already killed all of the Khanate guard. As soon as I breached the inner wall later, the goal to kill the Khanate Guard appeared but obviously, was not obtainable since well, they were not quite existing anymore.
After reloading one of the Autosaves from before, unfortunately the achievements did not unlock at all (reported on other instances).