I have seen shot pass through a unit without killing anyone occasionally, but nothing on a scale leading me to suspect a glitch. Observe that there is quite a lot of space around a soldier where a ball might pass through harmlessly. More often then not a ball will plough a gap through a formation as one would expect. The occasions where they don't just stand out more.

My gut feeling is that there is an overinflated expectation of lethality. Read more and watch less Mel Gibson movies and this should soon go away. ;)