Higher education institutions aim for deep learning and are increasingly providing their education through an online medium. SPOCs are a specific form of online education that has rapidly grown in the last decade. In this study, 11 SPOC instructors have been interviewed about the challenges they face when the aim is to promote deep learning. Five main challenges in achieving deep learning in SPOCs were identified: 1) Alignment in learning activities, 2) Insight into students' needs, 3) Adaptivity in teaching strategy, 4) Social cohesion and 5) Creating dialogue. These results indicate that SPOCs have distinctive challenges compared to other forms of online education. Instructors may have to place more emphasis on the social and teaching activities compared to the cognitive activities of the course. Instructors can take the results into account while developing and teaching SPOCs. Consequently, it shows the need for training in how to design and teach SPOCs.