I’ve playing a 3 vs 3 hard AI on mountain ridge map, the gameplay is about 3 hours, and after 2 hours, my allies stopped attacking, now their peasants also stopped doing anything, just standing on the map.
While the enemies are still attacking, and heavily cheating, however they can’t breach my outpost which is next to their village, but i also can’t do anyting because they attack/convert with all their 300 units if i do anything, as my allies are not attacking.
Why are my allies are disabled? They have plenty of resources. It’s a coincidence that the enemy AI is attacking, and only my allies are disabled? It’s not rare in game sessions, when the ally becomes totally passive, but not the enemy. Perhaps the cheat setting is too high? 
Less obvious would be better…