I have a Dog Model that I rigged from scratch. I used spline IK constraints for the Eyelids and Lips.
Whenever I move any Ctrl Bones that are hooked to the related bezier curve, the movement of the other closest ctrl Bones hooked to the same curve is almost unpredictable, they twist randomly and sometimes they move so fast that the Mesh deforms radically in that related area. So I have to click Esc to cancel the movement. But even doing that doesn't cancel the movement visually properly, to do cancel it properly I have to hit "rest position" and then hit "pose position". only in that way I can undo the mesh deform. I don't know what I am doing wrong.
I even can not move my Ctrl Root bone, otherwise the same unwanted deformation of spline Ik Constraints do occur again.
I tried with parenting/deparenting The curves to the Armature, didn't help. I also unchecked the Use Curve Radius under chain scale in spline IK constraint tab and used the "volume preservation" for XZ scale mode. It doesn't have any effect on this kind of crazy movements of the bones.