Not sure how to explain it, but check out this picture:
So if you look closely on the left strip of the image, the lighting is off (the strip is somewhat brighter than the rest of the image). This doesn't happen in every picture and I can't find more examples of it that quickly, but I can imagine this isn't the only one.
What can I do to find out whether it's something in my body, or something in my software? The lighting changed negligibly during the action of taking the picture, so I doubt it's a rolling shutter effect.
I'm using a Nikon D810 and Capture One Pro 10. I tagged the question very generally because "error" doesn't cover it, and "bug" doesn't seem to exist.