Part of scenes perform abnormally

[CCOSerika]

Hi, author. Thanks for the work on this project. I've test several scenes successfully on my custom dataset. Some perform well, like a toy dog(left img) and a horse model, and other meshes like shoes look fuzzy with an abnormal train process. The RGB loss increased sharply while other losses turned into zero at some irregular epochs, then it returned to normal at next epoch and the total loss converges as train goes on. I checked the dataset but found nothing. Any idea where lies the problem?