Advancements in Multimodal Learning Analytics (MMLA) have the potential to enhance the development of effective teamwork skills and foster reflection on collaboration dynamics in physical learning environments. Yet, only a few MMLA studies have closed the learning analytics loop by making MMLA solutions immediately accessible to educators to support reflective practices, especially in authentic settings. Moreover, deploying MMLA solutions in authentic settings can bring new challenges beyond logistic and privacy issues. This paper reports the design and use of TeamSlides, a multimodal teamwork analytics dashboard to support teacher-guided reflection. We conducted an in-the-wild classroom study involving 11 teachers and 138 students. Multimodal data were collected from students working in team healthcare simulations. We examined how teachers used the dashboard in 22 debrief sessions to aid their reflective practices. We also interviewed teachers to discuss their perceptions of the dashboard’s value and the challenges faced during its use. Our results suggest that the dashboard effectively reinforced discussions and augmented teacher-guided reflection practices. However, teachers encountered interpretation conflicts, sometimes leading to mistrust or misrepresenting the information. We discuss the considerations needed to overcome these challenges in MMLA research.