I have done exactly what you describe, with Vicky, and have had no problems.  Are you perhaps using one of the hand cameras?  This would be tied to the movement of one hand, making the other hand appear to move when it's really the camera that is moving.

A long shot, but when things don't make sense it's usually something you wouldn't suspect.

On the materials collection, only 6 & 7 have that capability.  P5 can only save a single material.  There is a button (6 & 7) that allows you to select the specific materials that are included in the collection.  You probably want to avoid that, as the invisible parts will still be using materials, unless you remove them.  You could end up with twice as many large maps unnecessarily.

John