Please try the following steps to check:
1. Try OSD Menu > DPC function:
2. Remove the back plate and take the PCB out. Clean the surface of the sensor with clean cotton cloth:
3. Remove the lens and clean the 2 pieces of glasses of the lens with clean cotton cloth.
4. If the problem persists, please try another lens. If another lens works well, then the original one has a problem. If the problem persists after installing another lens, the sensor has a problem.