I'm actually having the same problem it sounds like. I'll try to describe it in more detail. After about 15 to 20 seconds of flying the camera moves down and focuses on a lower part of the rocket, like if you were to scroll down in the VAB to look at a lower stage, and the rocket behaves as if the place the the camera is centered on is the center of mass. This can actually occur multiple times, it has for me atleast, until the camera reaches a point that it's centered ~50 meters below the bottom of the rocket again the rocket behaves as if where the camera is centered is the center of mass. It seems to only happen when the multi-joint parts are equipped on the ship. I haven't tested whether this happens in v4.1.1 yet but I'm about to start. I'll post if it happens again. Other then this new bug I love this pack, thanks for making it!!