For educators, identifying and characterising problems in their teaching practice is essential for triggering inquiries into their practice. Knowing what educators consider problematic is essential for generating strategies for situated approaches to help teacher educators manage their problems and promote professional learning. In this study, we report on qualitative research with the aim of characterising the types of problems of practice that 43 Chilean mathematics teacher educators identified in their teaching. We adopted an ecological data collection approach to investigate teaching practices. The source was a set of open answers from an activity performed in an e-learning course to develop mathematics teacher educators' skills to investigate their teaching practice. Based on content analysis, we identified three types of problems manifesting similarly in beginner and more experienced mathematics teacher educators, focusing on prospective teachers' difficulties or mathematics teacher educators teaching practices. Mathematics teacher educators also propose situated approaches to address these problems, based on evidence provided by prospective teachers. These problems highlight the challenges that mathematics teacher educators experience in their work and their professional development needs across all stages of their careers.