Outsourcing runaway.Outsourcing runaway.
Beginning
It may be beneficial for the advanced civilization to outsource all manufacturing to some less civilized place like Earth for instance, where work is cheaper, work safety worse, ecology can be more dirty and these locals still have some brains, even if much inferior. Lower level of general civilization may not matter much, as the qualified engineers, first machines and ready designs would come, making the production possible. Later, however, education will start catching up, making outsourcing even more attractive, as cheaper locals will be able to replace larger and larger proportion of the foreign engineers.
Overcoming of the self-correcting market force
Of course, at some point the free market would shift making outsourcing no longer so profitable. However if the government of the pure planet is strong enough, they may intentionally distort the market, by buying some useless nonsense for huge money from the "higher race". They would actually pay this money for the price scissors to stay and the further technology transfer to continue.
Of course, the higher race may also notice something going wrong, but the current situation may be useful enough for mighty ones to use they powers for making others to shutdown.
Total transfer of the technology
Eventually all manufacturing may move into that cheap and dirty planet, closing the former factories first, and then also moving the research departments closer to production. Ultimately only the managers may remain in the former place, but also management can be outsourced and is more efficiently when not done through interstellar distances. Hence eventually we get one civilization making everything for another, just on the basis of some agreements signed generations ago, and few very rich representatives of the once-advanced civilization that still benefit a lot from all this. And the advanced race failed to notice that not just they passed over all technology they have to that they thought it is just a planet of slaves - they have lost this technology themselves.
It is not difficult to predict that comes next.