The Disappearance of Mr. Davenheim - S2-E5
Continuity mistake: When Poirot does the newspaper trick for Miss Lemon, the final reveal has him present the newspaper holding it between index and thumb in the front view, index and middle with the thumb sticking out in the back view. (00:42:10)
What Price Gloria? - October 16, 1961 - S2-E4
Continuity mistake: When Sam goes out of the window to save Gloria, part of the ledge breaks off, but in the near shots it is broken off almost to the corner near Gloria, while in the shots from below most of the ledge is still intact. (00:35:45)
Abra Cadaver - S3-E4
Visible crew/equipment: At the beginning of the episode, when the brothers chat around the central morgue table, the boom mike appears above the table, on the upper side of the screen. (00:04:55)