During cooling the sharp phase boundary becomes much more evident due to avalanche behavior, where the phase boundary became pinned during transition (Figure , Movie S2). These avalanches follow behavior seen in inorganic martensitic transitions, where defects in the lattice, such as dislocations, create a local free energy minimum and corresponding energy barrier . The resulting rough free energy landscape causes the boundary to move in a series of jerks and requires thermal fluctuations to jump over the defect barriers. As mentioned, the avalanches were found during cooling, which is clearly observed as plateaus in the crystal intensity during the temperature changes (Figure ). This suggests the initial heating transition may be resulting in an increasing number of defect sites within the crystal that cause avalanches in subsequent cycles. However, despite taking several seconds, up to minutes, to become unpinned, this typically does not change the speed of the transition as each avalanche still occurs within less than one frame of the video (Figure ).