ZBrushCentral

Help with zbrush animation please

Hi,
I’m very new to Zbrush but have had great fun playing with the program - Its absolutely fantastic and has been such a help to my work as a medical artist.
I’ve figured out how to animate subtools with the move brush using the Layers in the Tools subpalette (like tensing and relaxing a muscle). But I can’t seem to just rotate a subtool (humerus head in the scapula glenoid cavity) and record it as a movie. If I rotate the humerus and record it as a layer, then when I play it back (move the slider on the Layer) then it not only rotates but scales at the same time! Maybe it only works with the move brush rather than the rotate button (top shelf).
Is this the territory that crosses into Maya?
Also - as added fun and games I want to rotate the humerus and make the muscles move with it. I tried using contact points but failed miserably.
Have I moved off the Zbrush reserve?
Thank you for your help, and for such an amazing program - its been a life saver!
Cat