Are you using fluorescent or LED lighting? If so the the problem is Pulse Width Modulation (PWM) of the light source and the scanning nature of the camera's light sensor. Basically, The lights are flashing on and off faster than your eyes can see but the camera sensor can pick up that flashing during the course of a single exposure . For reasons I don't know, this banding problem shows up in lowlight close-up pictures. The solution is to play with the shutter timing or use a light source that has no PWM, that is continuous in its output.