I don't know if this is happening to anyone else, but for me the AI of westphalia and wruttemburg just spam line infantry and try to take my fort as France. They've never made a single cannon to attempt to breach the walls. It ends up just being a boring fight where they just run to my walls, I kill them, rinse, repeat. They even field armies of 4000+, all line infantry. I still win with under 900 men.