Interesting, never had that myself in Survival (or Alpha). Kulak series have relatively short range... but not that short.
And this "moving to the right" part is really odd - are you saying that you have to aim NOT at the mob but somewhere past the mob, to actually hit it?
There's been a few mobs that had their target boxes little out of place but then you had to shoot higher, never to the side. Weird stuff, it sure sounds like a bug... got any screenshot, this would help a lot in this case?