I don't know what exactly is causing it, but these Radious mods are the only ones i'm using and sieges are seriously bugged. Made holes in a city wall yet my men cannot walk through the hole, lots of streets cannot be walked down. My ally assaulted a city from sea, all my men are blocked at a single point, there's two side streets i normally could go down but no, not with this mod.
I know it's this mod as i've played over 1500 hours and never ever had this issue before i installed this mod.
I like the mod, but city assaults on it are dreadful.