Renderred image with black walls

[KevinZ-01]

Hi, I am using the codebase to run objnav on hssd / procthor dataset. In procthor dataset, the rendered image is sometimes with black wall, black counter like this

In hssd dataset, the rendered image usually has a gray wall, black objects like these:



The image quality is not very good.

I wonder if this is normal or is there something wrong?