Here's a video I took that shows pretty well the issue with swing radius in Bannerlord. You can see me ready a right swing, and upon releasing, hit the shield of someone who is behind me and to my left. The literal exact opposite of the swing I am trying to do!!
Its also incredibly inconsistant when that happens. Sometimes you'll hit the guy behind you, other times it'll wrap around the guy in front and hit the guy behind him. Collision for walls seem to be messed up, the same thing happened in warband alot where a two hander would swing straight through the walls as if its made of paper.