~While fighting a siege, I'm the English, the AI's Milanese, I had an irksome one. They brought up one set of ladders, one ram, one tower. I got lucky and destroyed the ram before it got to the gates. Up comes the tower, up come the ladders. Troops start up the ladders, I meet them with my troops. Suddenly, the AI abandons the tower and tries to send every one of its troops up the ladders simultaneously. The problem is that they won't use the ladders - no more troops are coming up, but hundreds of them are in tight little packs at the bottoms of the ladders milling around. For whatever reason, this caused my CPU usage to spike, dropping me to 2 FPS (I'm guessing an AI looping issue, as pausing brought me back up to 60 FPS.) I ended up finishing the battle at a single frame per second by riding my general out of the gate and back and forth past the clusters until they routed one by one because of the presence of the cavalry. Even after I brought out all of my troops, they ladder mobs refused to budge - they just sat there and got chewed up by my in-the-open longbowmen.

~Another siege. I'd just taken a castle, and hadn't had a chance to repair the walls when the Spanish attacked again. I get the 'spy opened the gates' message scattering my troops all around. Unfortunately, two of my units of longbowmen were placed on walls that had no exits - sections of wall completely cut off from towers by my previous bombardments on the far side of the castle. This effectively denied me the use of a third of my missle troops for the duration of that battle.

~Speaking of which, in that same battle, the AI decided they were better off shooting ballistae at my intact wall rather than coming in from the side (in their deployment zone) with already destroyed walls and towers.