Hello,
Currently in some of my campaign, after passed the 2 "Upgrade troop" tech, some of my unit just disappeared and never could be accessed against, like the Khwe Emp, after researched the 2nd one, all heavy spearmen disappeared and made me hard to conquer powerful Euro factions due to their unstoppable cavalry charges. And some high end cav of Aybid also disappeared.
Is this a bug ?