I'm assuming you're watching them both on the same monitor.
If you shot the 4K in manual focus mode, it wouldn't be weird to shoot out of focus footage. It would be a little hard to do with such a side angle lens, but if it was set to wide-open aperture, then touched something in the screen that was near to the lens (even if by accident, it would focus on that distance) then shot mostly distant objects, it would be out of focus.
I wouldn't make any solid determinations without testing things out though, to be sure you have proper focus on shots that seem not very sharp.
Chris