@NguyenKhoi 

Hi,
When the camera is installed next to the wall, if the angle is too biased towards the wall, the infrared light reflected back from the wall may be too strong, and the wall will be overexposed. If the wall is overexposed, the camera will reduce the shutter exposure time to maintain the overall average brightness of the screen, so that the other part of the screen will be too dark. Without affecting the monitoring, you can try to adjust the angle of the camera, make the wall area in the picture as small as possible, and check if the monitoring image will be clearer.

Best Regards.

  @NguyenKhoi 

Hi,
You can adjust the angle of the camera to make the wall area in the picture as small as possible and check if the dark area will be brighter. 
On our end, I'll log your suggestion and forward it to the related team to evaluate, and we will continuously improve our products and deliver the best performance possible. 
Best Regards

  @NguyenKhoi 

Hi,
Thank you very much for the shared video clip. 
Can you help collect the detection type you have enabled on the Tapo app(such as motion, person, etc.) and the sensitivity you have set? I'll forward them to the related team for further analysis and improve our product.

Best Regards

  @NguyenKhoi 

Hi,
You can try to set the motion sensitivity to High and check if it will help in this case.

Best Regards