Porosity shrinkage is a most common and avoided defects of die casting process. In here, the casting was built using high pressure die casting method.
There were a lot last solidified area of casting part. Which was separated and could not get supply in certain phase. We simply could limit solidus temperature for better visual. The results could be overlay with hot spot, ensuring the areas was tend to high in temperature and some of molten still were on liquidus state.
Proper cooling might needed and should be take a die construction an account.