My apologies for not having an error log, but my Logs file is completely empty for some strange reason.
Recently while defending Oldenburg as Cologne from the Danes, I found a glitch with the walls. I was facing two armies, one to the north and one to the south. The north army was attacking and had the siege equipment, so I put all my forces there. After I defeated them, I noticed that even though the southern army had no ladders, they'd managed to climb up the walls--even their cavalry!
Most of their units that climbed the walls got stuck on an invisible wall at the edge, but some drifted in. I eventually defeated them, too, but while the game was going through the other factions' turns, I got a CTD and all progress was lost. So I reloaded and played the battle again, and just like last time, the enemy glitched up the walls. The CTD error persisted as well.