This is an issue that can happen with the auto exposure and the DRC setting on the camera.
Using the (On Screen Display (OSD), navigate to Exposure and tune as follows you can watch the issue disappear...
- Set Mode to Manual
- Set Shutter to <anything>
- Set DRC Strength to 0 (zero)
- Slowly lower the Gain to 0 (zero) and you can watch as the artifacts disappear.