I no longer have the 50/1.2 but do recall that the detentes were not as pronounced as other MF Nikkors lenses of mine. Perhaps the depressions are shallower, the sides less angular or the 'spring' (flat, leaf-like) has less tension or the 'v' is not as angular as others . Presumably your lens is fine, being brand new. For a definitive answer one would have to disassemble the lens and inspect. Not worth it.
"When moving from one full stop to the next, after the tactile 'stop' has been reached the ring has play back towards the previous direction of rotation." This may be due to the v-shaped bend of the spring coming to rest not in the bottom of the detente but just beyond it, requiring a slight reverse motion to seat it in the bottom. (This is a bit like card-tricks over the phone but the best I can do.) This ever-so-slight reversal to seat the spring is also common.
The advice given by LJ is very good: "Point the camera toward you...see that the aperture changes with even with the most minute adjustments." You can do the same with the lens detached from the camera and a bright light behind it to detect movement of the blades. Lastly, re: the tiny bit of ap ring movement beyond 1.2, that is common but doesn't translate to an increased aperture (bummer...would have been nice to have a 50mm f.8!). You'll notice the blades don't open further with that additional movement of the ring. Alrighty then...back to shooting!