Its actually more than just a Nikon issue, tactical turrets will do this if there is not a lock in place. I been messing with a 1-4x24 this weekend and it also has this same issue. Thought about the taping it down or tapping it to put a set screw in it as for most shots I will not have to move the turrets at all once zero'd. In most cases tactical turrets are way over rated but they look cool and scopes sell that have them, not because most people know how to use them or really even need them. JMO.....