Answer:

Because the egg yolk contains iron, and the egg white contains hydrogen and sulfur. When eggs are cooked for too long at high temperatures, the hydrogen and sulfur in the egg white will have time to react to create hydrogen sulfide gas. This gas continues to react with iron and forms a gray-green layer around the egg yolk - this substance is called iron sulfide, an insoluble compound that is not good for health.
When eating eggs that have formed this green layer, users are prone to bloating, indigestion, and fatigue. In some sensitive cases, this substance can also cause symptoms of diarrhea and digestive disorders.

It is best to divide the portion into small portions and store it properly. When needed, only take enough to heat. Only boil the eggs for less than 10 minutes, enough to cook but not too long. The eggs can then be added to the braised meat dish right before eating to avoid having to reheat many times.

Instead of leaving eggs in the pot of braised pork while it is reheated, a better solution is to just freeze the braised pork and boil fresh eggs each time to eat with it. Freshly boiled eggs may taste less delicious, but they are much safer than eggs that have been reheated multiple times.