NSA seems to DQ people on the poly chart results.
I took the poly five times (oh no, now they know who I
am !) and finally "passed" it.  True, after NSA has tried
to trick you, any derogatory information will be sent
to the DoD/DSS, to look at, for your TS clearance. 
However, as far as I know, the DoD/DSS does not look
at the poly charts (for good reason).  As
anti-polygraph information becomes more available,
NSA's amaturish and scripted tricks will become less
effective.

Mine is a very long story.  Thinking back, I did not have
a post-test interrogation, after my fouth, or fifth;
however, I did not pass the fourth, so go figure.  I am
an ex-NSA employee, now as a contractor for another
Intel agency.  Because I had some personal issues,
even though they were over two years ago, the NSA
just sat on my adjudication, until I gave up.  They are
absolutely security crazed, to the point of paranoia.
If I were you, I would say to hell with them, and go 
somewhere else.  Getting your TS clearance, from the
DoD, is so much less painful (you are interviewed,
not interrogated).  From what I have found, going
"across the bridge" is a much more pleasant option.
NSA can leave a bad taste in your mouth, plus you get
to work in a dysfunctional environment.  I am glad, that
I no longer have to worry about those creeps !