The description sounds quite like what I experienced. I gave up during my second polygraph 3.5 hours into it. After the first one I felt like complete crap. I was nervous going into the second one but felt a little more confident because I had a better idea of what to expect. So when they get into the "you didn't respond well to question X" part of it that was to no surprise.

I made me throw in the towel was after the person administering the test stepped to "talk with superiors." I just thought: I'll have to do this every couple of years to maintain employment at the NSA. Do I  really want to do that? Do I really want a bottle of Mallox in my desk drawer for the rest of my life? And the answer was no. So I gave up.

The other thing is most people DO NOT understand a polygraph. They think there is total truth to it. 100% accuracy. What I learned from the experience is that a polygraph is a way to interrogate perfectly innocent persons. I was a teenager at the time I took it so I thought it was somewhat silly to assume I was running some network of people attempting to overflow the US government. I suppose I understand why they do it. But it's not a perfect system. And people like Aldrich Ames and Robert Hannson slipped through and caused quite a bit of damage to the US intelligence community and between the two of them basically eliminated quite a few double agents in the Soviet Union. But again a lot of people I tell: ya I have had a polygraph and I don't think I did well. And their response is usually haughty either because they are overconfident and believe they could "beat" the polygraph in which case they are mistaken because it's really about interrogation and less about truth (in my opinion). And the other case is people who COMPLETELY believe in the polygraph (because they saw it used in some TV show) and think you are some type of domestic terrorist.

Anyway. Good Luck. I would recommend trudging on no matter how many polygraphs you have to go in for.