I see nothing wrong in this video all I see his him walk in the door with someone behind him they both look left and fire shots and by the looks of the slowed down version half of the shots from both of them wasn't even at you but the fucked up hit boxes gmod has makes it hit you anyways. I'm not sure why you slowed the video down or made it short I recommend you post a little longer one next time and or provide us with a unedited version. You said in your post that you see twitching I don't see that either or any fast adjustment of the aim its just like I said most of the shots wouldn't of hit you if gmod wasn't messed up like it is.