Welcome to the forum Griffin. I don't have a NX10. But on the Fuji X10, when using the panorama function, the exposure is locked in during the start of the sweep. In another words, assuming I'm sweeping from left to right, if the scene looks a little dark on the far left, by the time I get to the middle and right sides of the scene, which have better light, the middle and right sides will end up overexposed. On the Fuji X10, aperture and shutter speeds are controlled by the camera when using the panorama function. I think I can use the exposure compensation button to adjust, but it's been a while. But even if I use the exposure compensation to adjust, exposure is still locked at the beginning of the sweep.
I just did a search for your issue on Google. Didn't find the answer. But saw this Youtube video on a Korean website. This person has the aperture at F3.5 and shutter speed on 1/60. So the camera either picked something different from your default, or the user picked it himself.
SAMSUNG NX10 ver.1.30 panorama - YouTube
Sorry I couldn't' be more helpful.
We have at least two NX200 users in this forum. Maybe they'll be able to help.