This study examines a Mixed Reality (MR) simulation aiming to train first responders for mass casualty incidents (MCIs). The focus is on how trainees and instructors use workarounds to address uncertainties, and technical glitches during the simulation. Advancements in MR offer new approaches to MCI training, either replacing or complementing traditional methods. Using observations, audio and video recordings, and interviews, we analysed interactions through Goffman's concepts of ‘frame,’ ‘footing,’ and ‘rules of irrelevance. Findings show that participants in this MR simulation use a range of workarounds, to deal with glitches that arise in the training system and uphold the simulation, bridging gaps between real-world tasks and the MR simulation. Workarounds can be understood through the participants' framings of the situation, and how they shifted footings and frames. Findings demonstrated the importance of considering which representation from real-world work practices needs to be included in the simulation to ensure workarounds do not hinder the intended learning objectives. To mitigate this risk, organisers, instructors, and trainees must develop and deepen their competencies and understanding of the pedagogical underpinnings of simulation practice. These insights underscore the importance of viewing MR simulations as distinct practices with their own logic and conditions.