The transcendental deduction of Kant is on shaky ground. He himself rewrote it in the second edition. The idea is to show that after he has first given proof that reason and empirical knowledge have two different sources, then he wants to show that in spite of that, they work together to give true knowledge. I am thinking that the Friesian idea of a deeper source of knowledge [immediate non-intuitive knowledge] gives a answer that is almost implicit in Kant himself. For even in the second edition of the Critique,  he only shows that pure reason and knowledge based on the senses must work together, but not how.