should valves rotate ?

Unless you're using springs that are not made by winding into coils, the valves are going to rotate to some extent over time. It's not a sign of loss of valvetrain control, but a sign that as a coil is compressed and released a rotary motion is induced in it. Sometimes (over some rpm range for each possibility I'd imagine) the retainer will allow the spring to slip, sometimes the shim at the base of the spring, sometimes the locks will rotate around the valve, and sometimes the valve will turn. The beehive spring would help eliminate this to some extent because of the differing frequencies occuring along it's length. one might cancel out another. By design or not - valves may rotate and there's not a damn thing you can do about it.