I suspect a slight rotational movement is normal, it won;t effect the focal plane so it shouldn't make any difference.
Visit my Nikonians gallery.
Copyright © Nikonians 2000, 2013
All Rights Reserved
Nikonians®, NikoScope® and NikoniansAcademy™ are trademarks owned by Nikonians.org.
Nikon®, Nikonos® and Nikkor® are registered trademarks of Nikon Corporation.