Un fortunately the video starts after 2 of the wheels were already out of their sockets. To me this means the stems of the casters were not pinned in place. The floof was clean and clear of debris as far as I could see so I 6think they tried to move the scaffold without unlocking 1 or more of the wheel locks 2 guys giving it a shove to move it would have been enough to cause it to tilt slightly and allow the caster stems to fall out. From there it was all over but the pain.