Do you have a regular mouse you can test, in case it’s a tablet issue? I have heard of people having disappearing cursor problems, but it doesn’t seem to be that frequent.
If you got your figure shaped using the supplied morphs any joint repositioning should have been taken care of for you. Two things to look at - first, are limits on - if you use the parameter slider to move a joint, does it have a limit to its travel or can you spin it round and round, with the slider jumping back to the middle when you release the mouse? Second, how are you posing - saved poses, using the sliders, or by dragging on a body part in the viewport?