After Mannix' Blue 1974 Camaro is sandwiched by two Semi Tractor Trailers, there is considerable damage to the front & back. A few moments later when Mannix is talking on his car phone, he drives off, and the front & back have no damage.
When Mannix and Ruth (Helena Carroll) discuss Harry's notebook you can see white tape on the kitchen floor. These are actors marks for camera angles.
At the 21:00 minute mark, Mannix is talking to Mr. and Mrs. Gilbert Kordic. The reflection of one of the camera crew can be seen behind Mannix's left shoulder, in the bay window door.
Throughout the episode, Vincent Demorra's first name is consistently mispronounced "Vincente". The equivalent in Italian is Vincenzo, and the non-existent "Vincente" sounds more like the Spanish version, Vicente, but there is no reason why an Italian-American should have a Spanish-sounding forename. "Vincente" does not exist as a real name in any language, and the only known usage of it as a fabricated name is by Vincente Minelli, whose real name was Lester Minelli.