While I don't use an underworks binder, but rather a women's 'love handle' type slimming binder, my comment might be invalid, but in any case. Since starting to wear my own binder more I have noticed some things in regard to nausea. If I'm stressed out anyways and am wearing the binder for even as few as three hours, I begin to feel nauseous and sometimes too ill to really even more about. The other thing i've noticed that when not feeling gross anyways, I can go for very long periods of time in my binder (longest time being about 8-9 hours) without feeling sick UNLESS, the binder bunches. My binder slips over my bust and ends around the end of my rib cage and i've found that it may sometimes roll up at the bottom (simply from lots of movement throughout the day with no privacy to correct the problem), this pressure very quickly contributes to a feeling of illness and i'll usually start feeling ill soon after, but simply running off to the bathroom and adjusting the binder takes the pressure off my ribs and organs (I guess?), which relieves the sick feeling. So I suppose the issue with what you experienced is that maybe your binder was just putting pressure on some sickness triggering areas? Try stepping into your binder and spending a bit of time figuring out how to position everything in order to get a more comfortable fit, would be my suggestion. Good luck!
Edit: And I just saw that you've already addressed 'rolling up' as an issue. I don't know if this would work, but they do make the 'slimming' body binders for women (one of which I use for breast binding) and I'm pretty sure they make them in variable lengths. What may work is finding one that goes down far enough that it won't start rolling, or even long enough that you could form a kind of sewn latch to connect to pants or underwear (though that could result in an glorified wedgie... The only true problems I am finding with my current binder is that it descends if I do anything over a fast walk, and it roles every now and then, resulting in the nauseous feeling. However due to my desire to not give up hope on this binder, I'm currently in the process of creating shoulder straps (just like those found on any normal FTM binder) in order to stop the decent and the awkward 'up-the-shirt' maneuvers to try an fix it. o_O