This is most likely banding from flickering artificial light interacting with the camera’s sensor readout (rolling shutter), rather than a fault with the camera.

It’s commonly seen under fluorescent or some LED lighting, where brightness pulses at the AC mains frequency. If your shutter speed catches only part of that cycle, horizontal light/dark bands can appear.

Ways to reduce or avoid it:

• Use slower shutter speeds that match the power frequency: typically 1/50 or 1/25 sec in 50 Hz regions, and 1/60 or 1/30 sec in 60 Hz regions.
• Test different shutter speeds and increase gradually until banding returns.
• Add non-flickering light, such as daylight, incandescent light, or flash.
• If your camera offers an anti-flicker setting, enable it.

A good test is to photograph a plain white surface under the same indoor lights at different shutter speeds. If the bands change or disappear as shutter speed changes, flicker is the cause.

Some LED lights flicker more than others, so the problem may only appear in certain locations or with certain fixtures.