Visible crew/equipment: During the long car chase, after Freya tells Matt that he's an awful driver Matt makes a sharp right turn and the car chasing them stops short, and when they back the car up we can see the reflection of a crew member wearing a hat (perhaps the cameraman) on the car window.
The Wrecking Crew (1968)
1 visible crew/equipment mistake - chronological order
Directed by: Phil Karlson
Starring: Dean Martin, Elke Sommer, Nancy Kwan, Sharon Tate
Revealing mistake: When Matt and Freya are attacking the compound, at one point he goes outside and throws a "hanky panky" grenade at what looks like a garage door. He throws himself over a hedge and a moment later the grenade explodes. When he is getting up, the "ground" is obviously a cushion covered with fake grass.