I wonder if anyone is going to apologise to duraace for the original scorn with which he was greeted by some?
Sort of reminds me of politics: there are those who simply refuse to accept that their gods can have huge, plodding, feet of clay.
It is not uncommon for someone to bad mouth equipment whilst being unable to provide proof, such is life. And the original post was very sketchy, and did not provide the amount of detail required to determine what the problem was. However, a bit of thought, and some tests, from numerous people on the forum have solved his issue, so he should be a happy bunny, or at least a more informed one who can make his own decision about the lens in question.
And Duraace might like to thank me for suggesting what the problem might be, describing a way to test for it without need of a ND filter and suggesting a simple fix. After all some other people including NashvilleMike originally said they could not see the problem, or could not performs tests due to not having a 10 stop ND filter. (Then again, I'm not one of the forum 'experts'.) And he might like to thank NashvilleMike for carrying out the suggested test, confirming that it is due to light leakage from the sides, and confirming that the suggested fix does work.
There's no need for masking tape which could get gunk on the lens and into the mechanism. A simple sleeve (card with black felt on the inside) should work and could be stored on the lens.
I have to agree with those who say that this is a design flaw, and Nikon should be alerted. As to whether or not this is a "not fit for purpose" flaw, that I do not know. Not many people carry out such exposures. I would say it is not a reason to claim a refund from Nikon. Just my opinion, and others may disagree.