What are the problems that may arise while carrying out sustainable development?

Income equality and environmental degradation.

Explanation:

When nation reach a sustainable development state, It already implemented several optimizations that maximize the economic production. (such as using latest technologies in factories, most cost-efficient materials, etc)

These optimizations tend to lead to an increase in overall national income.

But, the largest portion of that income will be given to exclusively the owners of the factors production. This will gradually cause income equality in the country. On top of that, the new technologies that required for sustainable development tend to create emission as a side effect This contributed to the environmental degradation.