Legend of the Lost Art - S8-E10
Revealing mistake: In the cave, after Magnum bangs on the ground the hidden door opens, and when he lights another torch flame, the end of the cave set is visible at the right side of the screen. Also, in the previous shot Magnum is not wearing his watch when the door opens, then it suddenly appears on his wrist when he crawls through the doorway. (00:03:45)