The Night of the Death-Maker - S3-E24
Continuity mistake: Towards the end of this episode when West gets into the casket, the width of the head area is wider than the foot area of the casket. There are only two circular hand grips on a side. When the two monks are carrying it to the furnace, the casket is symmetrically shaped with the head and foot areas being the same width, and there are three round hand grips on the side. Right before the third freeze frame when the monks are in front of the furnace, the casket is back to the original shape with the head area wider than the foot area.