Y rotations often get wacky after a figure is repositioned and posed, but not sure why yours is doing that.  In either case, there is a quick and dirty fix.  Load a ball prop and place it in the middle of the hip, using translations only, no rotations.  Select the human figure and go to Figure--Set figure parent, and make the ball the parent of the figure.  The ball will rotate normally, and the figure will follow.  Make the ball invisible, of course.

John