treever, hi

looks like some kind bug to me.
How it happens I cannot say. I suspect some kind of bad interaction with putting on/off artifacts.

For explanation, lets say you enable Dif Mod and set the AI on "Normal" and the Payday to day 20.
That means for 20 days nothing will happen and after day 20 the AI will gain 1 random stat point per hero level up. If AI hero has reach level 40 that means in worst case all the primary stats of AI should be increased by 10 points on average. In no way it can explain an attack value of >100.